2 hours for me. I would rather under smoke than over smoke. I use a 6" A-Maze-N oval tube in my 3-burner Genesis II.
I have noticed ambient temperature has a big effect on how much smoke some cheeses will absorb. Cheese smoked at 60*F for two hours is just right for my family but if it is 35-40*F it takes much longer. So, two hours at 60*F and I adjust time from there.
Here's what I do may be right or wrong but works for us. 4 hours with apple pellets then make sure the cheese is dry no condensation or anything then vacuum seal and wait 2 weeks to allow the flavor to meld and mellow.
Some don't wait the 14 days but we like it better that way
6 to 7 hours for me, but I'm using an A-Maze-N sawdust tray. I start sampling one sacrifice piece at 4 hours and try and judge the perfect flavor over the next 2 or 3 hours. I do a counter rest for a few hours and set it in the fridge on some peach paper. Bagging can cause condensation, which is not good. I'll tent it with clear wrap, often with a paper towel over it, again to stop condensation. The next day I do another taste test, and sometimes I need to give it some more smoke, usually 1 to 2 hours.
Most hard to semi-soft cheeses I'll do 3-4 hours. However, pepperjack in particular I've had really good success with up to 6-8 hours on that. Done in two 3-4 hour smokes with a day to rest in between. Gives a really prominent smokey flavor but doesn't overpower the peppers at all. Also with the double smoking you can switch up your flavors. I've done cherry/hickory on pepperjacks before and it turned out awesome. Especially if you then grate that into a mac and cheese.