Schedule

Bed-time <= wake-up time - 8 hours

Last {sugar caffeine alcohol | nicotine} time <= Bed-time - 1.5 hours

NOTE: I think the last sugar/etc. thing tied to 1.5 hrs depends on the amount of substance.

Also, I think many people are healthier on ~7.5 hrs of "good" sleep than on 9hrs, so we might want to adjust this to reflect that.