Well there were separate 15 minute time slots for each game, so that implies 40 hours per game.

FWIW, in the past Larian has tended to be conservative with their playtime estimates (D2:ED had an official estimate of 40 hours, but exploring everywhere and doing everything took me 75 hours in my first game; some others were faster, especially if playing on lower difficulty settings).

I'd also prefer quality over quantity, if there must be a trade-off. Within reason, longer is better, of course, if quality isn't sacrificed.