Sunless Citadel took, hm, 3 five-hour sessions, IIRC, and we played every 3 weeks, so, a month and a half. Now, we're halfway through Forge of Fury with 3 more 5-hour sessions, but we played a little less this summer (or played other campaigns), so I think we started FoF in mid-july, so it's been 2 months and a half for half of FoF. I plan on playing all the modules... It's going to take a while...
AR