Depends on what temp you are cooking at. I like to go a little higher with chicken to keep the skin from being rubbery. I would say a 3ish hours at 275 - 300, but that's just a ballpark - keep that thermo handy and good luck!
On the drum I get em done in the 2 1/2 ta 3 1/2 mark fer a time guide, yer temp probe will tell ya when there done. I take mine ta the 165° ta 170° mark, give em a nice coat a 50% butter 50% honey glaze an let em rest 15 ta 20 minutes. Fine eatin.