I found that I burned out on P90X: the combination of a busy schedule already plus additional food prep time (I tried to follow the menu plan exactly) meant that I sacrificed sleep. And if you're doing intense workouts, sleep is very important. I could probably do it fine on a more relaxed schedule with an eat-healthy-but-don't-follow-the-meal-plan-exactly approach.

With Stronglifts, it's every other day for about 45 minutes including a bit of warm-up time. So far, this has proven to be a great pace for me as it allows me to still be quite busy with work, etc. while allowing sufficient time to recover in the off days.