It is not a simple black-and-white yes/no answer which is why I have several articles about No Contact. The main article about No Contact is linked in the first reference to No Contact and the others are in the related posts section after the article--for some reason this section is repeated, so they are shown twice.
As for other jargon I have tried to put links to articles where terms may need clarification. I had done this already, but just went through and added a few more. I use maroon for colouring hyperlinks, so just look for text that is maroon.

So should you contact or not? No Contact is a strict boundary that is only to be broken to end the boundary or when a boundary comes to an end of a pre-set time period or for emergencies--car accident, hospitilization... Child custody exchanges are not an exception and need a mediator if necessary. Most people go Dark when children are involved since a true No Contact boundary is not usually possible.
Suppose you are no using a No Contact boundary, does that mean that you contact your MLCer? No, not necessarily, it often means your MLCer will contact you and since there is no boundary you may choose to respond back. In a No Contact boundary if your MLCer tries to break it by contacting you (and many will) it means you will not respond back--not by text, email, phone...

I'm not sure if this explanation is helpful or not, hopefully understanding more of the jargony terms through the linked articles will help, but let me know.

http://www.midlifecrisismarriageadvocate.com/stan...

Thank you so much. What an excellent point regarding infidelity. In reviewing that I covered what I needed to cover, I obviously missed that. Infidelity is such a grande part of MLC--the overwhelming majority of male MLCers have some sort of affair--that it is easy to forget that there are those who do not.
I have added to that section of the article.

Melanie,

I don't think there are specific statistics like you are requesting. Personally I am not a fan of statistics and only wrote this article as a reassurance to LBSs.
Since we are each individuals, this is not like a controlled chemistry experiment; you can change the odds by how you react or respond to your situation.
It's great that he is still denying the alienator.
I recommend you head over to the forum and post your story and read the other stories. We change our odds when we detach and learn how to interact with an MLC spouse with grace.

I could give you a long list of suggestions, but I think it would be better to direct you to the forum: http://mlcforum.theherosspouse.com/index.php.
Go over there and read the stories others are posting, read the resources and most especially--if you feel comfortable--start your own story thread. Once you have a story thread you qualify for a mentor--OldPilot will ask you if you want one and if you don't answer I will eventually send you a private message asking.
The first step is detachment--hopefully you have made some progress toward that in the last two years, but if not please don't worry yourself about it; some learn what to do quickly and others find the advice after months or even years. What matters is what you do now.
Stop nagging and do not react if he tries to incite an argument. You need to protect yourself--emotionally, financially... but you also need to be kind even in the face of Monster--that often shocks Monster! It's a tightrope because while kindness is important, so is staying off the doormat and to do both those things is often a challenge.

I understand that after a few years during which you may not have known what to do and so you have begged and argued you feel like you've lost your chance. NOOOO that is not the case. Detachment is the first and perhaps most important step and the key to that--and perhaps Standing in general--is mindfulness. Hope is not lost.

This is an excellent question.
First, there really aren't exceptions to Standing because it's a personal choice and some Stand even if they are certain their MLCer won't return--they are basically Covenenat Keepers, though they will not use that term if their Stand is not religious.
But you really want to know if Standing is worth it with the goal of reconciliation and that depends somewhat on how you have been handling your situation: Truth Darts, Communicating your Stand...
In general, is an affair that has lasted in public for 6 years no longer in infatuation and is it likely to last?
No, though perhaps the odds are better for it lasting than the affair that is only 1-2 years old. And there are no guarantees, my step mother is still married to the OM and if he lives until next Valentine's Day it will be there 30 year aniversary--and I call the OM 'Daddy.' (He has terminal Cancer which is why he may not make it to February).
In your situation I am more curious about what you have done and said during the 6 years. Does he think you are accepting of the affair and just indifferent regarding legalizing your divorce? Or does he know you are Standing?
Being cordial is important, but have you been so nice and seemingly accepting that he feels no guilt? Or is it the opposite and you have been so angry and blaming that he wants nothing to do with you and sees her as a better option?
Or it could be none of those.
When he talks about moving things along, do you ask him to be more specific--use the word divorce?
As a Stander I would have commented back that it certainly was time to move things along and get rid of her so he can get back to repairing our marriage--though that was something that I would have been able to say because that sort of communication was an established part of our dynamics and my Stand. That is not something someone can say out of the blue.

But there are some gaps in there.
Don't chase, [GAP] but make sure he is safe, [GAP] but don't bother him. [GAP] Let them know you still care...
Those gaps are places where maybe you could contact, though the first try would be for the information to leek through the grapewine.
Sally Conway described Contact types also: DropIn, Droplet and Dropout correspond to Boomerangs (which I split into regualr and Clinging), In-n-Out and Vanishers. Vanishers vanish and if you are Standing with a goal of reconciliation No Contact is not meant to be permanent. So someone, someday must make a move. Close Contacters--especially Clinging Boomerangs--need a lot of reassurance rather than an LBS who keeps a distance. Yes, let them initiate (and Close Contacters will), but respond.
Aggravating them is not about contact of any kind, it's about relationship discussions and pressure and guilting or shaming them for the not being home or for leaving.

The MLC Time Clock begins at Bomb Drop. There are MLC stages before Bomb Drop, but nothing is really progressing and those stages may be indefinite time-wise.
Distant Contacters are different than the Close Contacter who often show us more of their MLC experience and so it is easier to give information about Close Contacters. So should he be over it soon? I don't know, and perhaps a more valid question (for which sadly my only answer is sadly 'I don't know') is will it end soon. Shoulds aren't about reality.
One of the things I have been wondering recently is if it is possible for an LBS to have some level of influence on the Contact Type--Distant vs. Close--of their MLCer. I think most of us are neutral since we don't know how to do that and so the MLCer falls more naturally into one type or the other, but if (big IF) type can be influenced, then I recommend influencing MLCers toward Close Contact. How, I'm still thinking through that.

Given what you have, YES it sounds like MLC, but you have not given a lot of information, so I could certainly be wrong.
I recommend that you read the articles and join the forum--and post your story. Participating in the forum may be the best thing to do for most people because not only will you get a variety of answers, you will also get support from others who truly understand what is happening--or at least know (let's face it, do we really understand MLC?) from experience.

Given that your husband is outside of the age range and his symptoms began well before Bomb Drop, I cannot say if it MLC, or almost tipping and could tip to normal again...
BUT
Changing your behaviour to more detached and distant is likely to produce the results you are seeing. Have you read the Pursuit & Distance articles? Here is the first of the Contact & Communication series: http://www.midlifecrisismarriageadvocate.com/stan...

You are Going Dark, as No Contact is about absolutely No Contact accept on rare occasions and with children such occasions are not rare. If you are more detached, you are likely calmer, stronger and more firm regarding boundaries with him. This will make him curious--especially since these qualities are attractive.