How does that make it fantastic or unrealistic? Ask some Holocaust survivor about the couple of years he spent locked up and tell him that it was insignificant.

Well, as you alluded in your opening paragraph, they'll go on like normal and lead relatively mundane lives with the Dark One out of the way. The excitement and adventure some of them claimed to crave back in the beginning were really just novel degrees of mundane-ness.

And you and I can go through every subsequent calender year fighting over what Egwene is likely to do in them!
I don't know. I think the notion of a decades- or centuries-long vocation dedicated to battling crises on this scale would be a different degree of fantastic and unrealistic.

Here's hoping. Otherwise I'm going to have to start posting torture porn fanfiction starring Egwene.

I believe I disagree with your central point, which appears to me to be an issue with the heroes being thrust into this conflict on a colossal scale that defies the imagination (and of which they themselves seem to rather lack a proper understanding - you notice that most of them are only concerned with their immediate issues and the crises occupying their present attention), at the mere outset of their careers and adult lives, leaving a long decline and anticlimax afterwards. Maybe it is done that way so that we can then imagine them building a better world on the rubble afterwards, each of us to our own ideal.

I also don't think we would be missing much by not getting the later years and I disagree with your apparent claim that we are only seeing brief moments in their youth, and that more significant things are to come for them. That may be true for some of the characters, but first and last, the series is about Rand, and I find it hard to believe that anything in his life to come will have more significance than the changes and events of the last two books.

I think that for the rest of the characters' lives, however long or short, the events of these books will define those lives and give shape and meaning to all they do afterwards. I cannot imagine their playing significant roles in the defeat of a malevolent deity and the reordering of the fabric of reality and then filing it away as an interesting youthful experience, like a summer abroad. For good or for ill, Tarmon Gaidon will not be the kind of thing anyone can forget, or grow out of. Just as the series implies or foreshadows Rand's destiny cheating him out of a long, happy and peaceful life as a reward for his heroics, so the characters that walk away from the Last Battle will be unable to forget it. Even if they are untouched in any tangible way, they will almost certainly carry a mental, emotional or spiritual equivalent of Rand's wound from Falme. Some of them will be unable to overcome the horrors and will become consumed by their experiences. Others will grapple with them and overcome and grow stronger for the struggle, but no one will come away unaffected or unchanged in a life-long manner. The Mat, Perrin, Egwene, Nynaeve and Thom we saw at the end of Towers of Midnight will not be the same characters as the ones who are still standing at the end of aMoL. Even if we were to see a glimpse of the world of WoT 200 years later, I would bet that those characters still living would be closer to their states a year or two past Tarmon Gaidon than the post ToM characters would be.