How long do you normally cook you baby backs?

[Keiferr]

Experiment and see what you like best. There a lots of ways to do them. "Best" is what makes you, your family, friends, and smoking buddies say "That there’s dang good!"

[RustyHaines]

PBC 2 racks hanging. 275 cook temp, 3 hours, sauce, then 45 minutes more. For 4 racks increase the cook time to 4 hours. They turn out eat off the bone perfect, not falling off the bone overcooked.

[Mr. Bones]

So, this is kinda a Trick Question, right? (Cain't really say that I've ever been particularly successful at "Normal")

All th above is very good advice, based on cookers/temps, etc.
Most usually, I do several slabs on one/more stickburner(s), wood fire, keepin my pit temp centered on bout 275°...
They usually run ~ 4 hours; I start gittin more active, checkin, bout 3 hrs, cause I've had a few try to be schneaky!