I get that. That makes a lot of sense to me for Barney, since he seemed like he really was tired of who he had been. But I can also see that when he failed (and think...he failed with Nora, then Quinn, then Robin), I could see him giving up....though I'd expect him to self-destruct, not snap back to being happy with that life.
Robin bothers me less because I never really felt like she evolved, more like she just got bad writing from around the time she started dating Barney the first time. ;) It didn't feel like character development with her for the last several seasons, but like they grafted a new personality onto her.