We've been playing the current campaign for over 4 years, started at lvl 4 and reaching lvl 9 tomorrow (fingers crossed). Granted, we're busy adults that get to play too rarely, so a better gauge is the just short of 30 sessions we've had.I’m also not sure how a 10-level campaign is short. Even at one session a week and leveling up every other session on average (both very generous assumptions in my opinion), that’s 5 months. Factor in any sessions that have to get cancelled and you’re looking at half a year, or a whole year if you play every other week.
I look forward to continuing the campaign. My greatest worry is that 6e will hit before we get to lvl 15!