RUFFHAUS, I'll speak to why I sometimes select games -- even gunboat -- with very long phases. Can't speak for others.
First, I've consistently been present on this site and engaged in games since I first joined. I have no reason to think I will not be here in another year or three when a game started now might finally wrap up, and so I rarely consider how long a game will run when I join it. I do consider, and I think this is more to your point, whether others that join the game will be able to keep their commitment. Now, maybe an examination of my game history would reveal my perception to be faulty, but after playing dozens of games 3+ days per phase, here and webDip, it hasn't been my experience that they have been more heavily affected by NMRs and CDs. True, in a game lasting a year the CDs might just be spaced out enough that I don't recall them once the next one happens, but again that's not how it seems to me. I think this also speaks to how bad the NMR/CD problem is in games of any duration. Unfortunately, they happen regardless, and far too often.
As to why I join such long games in the first place, there have been times in the past year that have seen me simultaneously taking 16 credits in school, working up to three part-time jobs, and playing in three bands, all while prioritizing my role as husband and father. There have been some grueling stretches. Diplomacy is not nearly as important, but it provides a great break from those things and a valued distraction from daily stress. I don't commit to press games when I can't follow through, so sometimes gunboats are my only reasonable option to have a few games going. Plus, I just enjoy them. And so, awhile back, I started joining and creating gunboat games of up to 4 day phases. Sometimes I've got time to ready up in all of them, sometimes I need the whole phase. I really don't think these have been more heavily impacted by people vanishing than short-phase games.
Aside from the problem of NMR/CD, I've found that gunboats are not nearly as affected by a long phase as a full-press game. With press, a week for retreat-build, over and over again, is indeed a recipe for lost momentum and sporadically shifting alliances.
Anyway, that's why I play them. Then again, I play just about every variation of Diplomacy I can discover or conceive. Even so, forced to choose only one set of parameters, I think my preferred game would still look much like yours. Good to chat with you, it's been awhile ;)
)
American Empire 1 on 1
)
)