I think between 1-2 hours for a game day is reasonable. A 24hour game day is way too obtuse IMO. One for the idea that as a working class member of society my schedule is defined by the pretense of line of work. If I was doing shifts I wouldn't always be active at the same times every day, however a large portion of workers have a FIXed schedule taking up 8-12 hours of their day at set times. Thereby making them always having the game being fixed to times they are not at work, missing a huge portion of game day time(a third to half the day).
As for time spawned monster, I love the idea. And guess what, Real Life has "time spawned" animals. Most animals are un during the daylight hours but we do have a fair number on nocturnal animal coming out at night. So OMI not having time spawned monsters in kinda unrealistic.
