I'm surprised no one has chimmed in here yet...
I'll give you what I've read from others on this site as I'm certainly no expert.
I think the general concencus is that the bisket is done when it's done. You know it's done when you stick a probe in and it slides in and out like the meat was soft butter.
Guys here refer to it as "budda"
From a temp stand point I think folks start checking for the budda feel around 180* or so with the understanding that a lot of the time it takes 200+ to get the budda feel.
Hope this helps.
2004 Weber Performer GREEN
Orange Super-Duper Fast
'08 Weber Genesis Gasser
SJG Tamale Pot Mini Smoker (SJG was a rescue)
and a Pyro FIL