Everything isn't all drama all the time. Whether it's a story or real life, people need time and space to step away from everything, take a deep breath, and just be. As IICIH mentions, there'll be time for drama later. Maybe I'm looking at this wrong, but to me one barometer (among many) of a healthy relationship is the avoidance of unnecessary drama.
True, but there isn't really a reason to show us that, is there? I assume Penny and Will are completely happy and maintaining their relationship well, mostly because we havent' checked in on them in a long time.
The flip side of that, though, is the degree of connection to the rest of the cast. Penelope isn't really close to any of the main cast. Sure, she works at CoD, but even Dora seems to forget that from time to time. For his part, Wil's really only connected to Sven (who we haven't seen) and otherwise only shows up when the story calls for beer and fancy clothes. Sure, we don't have to see every last time Penelope gets angry at Wil for leaving the seat up, but it's also not like they're close enough to anybody else to figure much in their stories except as window dressing.
Marten, on the other hand, has connections to the whole main cast (he is, after all, the comic's protagonist), and Claire is connected not only to Marten, but also the gang at the library, plus Clinton. Clinton aside, she's good friends with several of the people she's met. In other words, their relationship could be smooth sailing for the remainder of the strip* and there'd still be plenty of reason to feature both of them, since they'd presumably have an interest in what goes on in their friends' lives, and they offer support where they can.
*Not that I foresee it playing out that way, or think that it should, mind you.