Here's what I do when I want to plan on eating at a certain time. I'll use butts as an example. Let's say I want to eat at 6:00 P.M. on a certain day. I'll subtract from that time the following.
3 hours for resting (you can go shorter, but I do 3)
16 - 17 hours smoking (I cook at 225 degrees, know my pit and I'm pretty much on the money each time. But I do cook by temperature)
1 hour to "knock off the chill"
8 hours for my rub.
Toss in more time if you need to, but I just add those hours up, and that's how many hours before my planed eats that I get started with preparation.
As others have said, butts always stick at around 160, sometimes 170 and you'll almost think your thermometer is broke or your fire is not doing its job. Just be patient and when it jumps, it usually moves up fast after that.