- Moisture content
- Size/weight of the cut
- Number meats cooked simultaneously
- Number of times you peek!
- Fat to lean ratio
- meat aging (enzymatic breakdown of tissue, at least for beef)
- muscle density
- shape/thickness of meat
- pit temp and variation
- hot/cold zones in the pit
- air flow
- time between coming out of fridge and going into smoker (core temp of meat)
- ambient temps
- humidity
- shape, size, and composition of your cooker
- fuel type: Moisture content, BTUs, etc
You can control cook times to some extent with temperature. I've had outstanding (but less smoky) brisket at around 14 lbs trimmed in 8 hrs with a 'fast cook' method at 350 degrees: That's 2.5 hours unwrapped, then wrapped until internal temp of 203 then rest until serving time (1-4 hours covered with a blanket or towel or in an insulated cooler), but always the pull-off-heat moment is controlled by temp + feel not time.
I've also drawn out the exposed to smoke phase to 4 hours at 250-275, but those meats finished slower, pushing 8 hours out toward 10-12.
I don't know if that's what you were looking for Smokinchicken, hopefully it helps though...