I think worldsapart and I reached a basic consensus in opinion.
Mike is a cuckold, and a cuckold is someone that needs to be cuck'd to "get off" like a gay man needs to be with a man to get off. It's not just a kink to him, but a sexual orientation. And, there is a continuum to the scale. I would put mike at a level 9, which is someone that is comfortable and turned on with wife loving another man, getting pregnant, denial, and even putting him in chastity. I think we are all on a continuum, and perhaps it's even a sliding scale (I have been pushed down the scale a bit), but we have different breaking points or boundaries.
I also agree with most of what aguy4pleasure says.
A crisis point is coming. Yes, Scott would reasonably, at some point, give Jen an ultimatum. But then at some point, Mike would also give up or give an ultimatum.
You see Mike is a cuckold, but you can only enjoy (get off) being cuck'd by someone you love, and probably someone that you feel loves you back. For example, I have a wife that loves me, a girlfriend, that likes me a lot, and many female friends that are just friends.
When my wife cuck's me, it drives me wild. When my girlfriend cuck's me (she still sleeps with her ex), it turns me on, but not as much as my wife, because our relationship is not as strong. When my female friends (that are just friends and not sexual partners) "cuck me" (meaning they just tell me about their sexual exploits with their own boyfriends, etc.), it's mildly titillating, but does not do much for me.
So, my point is that Mike is still strongly attracted to Jen because he both loves her, she loves him to some degree, and he is thus turned on by her cucking him. If he stops loving her, and/or feels that she no longer loves him, she starts to become a "friend", and the excitement wanes.
If yet another female friend becomes a lover (Elaine) to Mike, and then she starts to cuckold him, well then mike would start to "get off" at a high level with her, and I think that might actually break the bond with Jen. Only at that point, would Jen really be "replaced" by someone that could give Mike everything he needs.
My only concern (question) is how Mike and Jen can continue to feel "connected" as a couple when Mike only really is together with Jen for a couple hours every 3 weeks? I get the thrill of watching Jen from across the room, but there is no opportunity in those public moments together to talk and really connect. That time has been extremely limited. As I say, it appears to be only a couple hours every 3 weeks or so. That lack of "connecting time" is what kills a marriage. I almost expect Mike to say some week, "Can't come this weekend, Jen. I have something else I gotta do. (Work? Elaine? Watching the Rangers take on the Bruins?)"