Well, if anyone cares to know...
My 15lb brisket was done in 15 hours. The temp in the smoker was 245-250* the majority of the time. I had to restock twice and each time the smoker spent about 30 minutes getting back up to 245, then continueing to climb to 260 where it would stay for about 15 minutes before settling back down to 245-250. I seperated the point at the 12 hour mark returned the cubed point to the smoker for burnt ends (which I plan to taste shortly). After an additional 3 hours (hour 12 to hour 15) between 225-245*, I pulled the flat and wrapped it up to sit. Dinner isn't until 6ish and I pulled the flat at 12:30, so it'll have a while to rest. I intend to check it at 4pm and stick it in a 200* oven wrapped in foil with a little beef broth if necessary.
The packer was 15lbs when I brought it home. My best guess is that I trimmed a solid 2 lbs of unnecessary fat before I started to smoke. Overall I'd guess that I was closer to about 70 mins per pound on this one.
Thank you again to everyone for the suggestions!
18.5" WSM, Large BGE, Backwoods Party
Blue BBQGuru DigiQ DX2
Blue Superfast Thermapen