Spider Venom

[Big B’s BBQ]

Just added a spider venom to my 26' weber kettle and did my first cook, beef ribs.  I used the SnS sear and slow. Covered remaining bottom grill with foil.  started a small chimney of natural oak coals. It filled about 6" of the slow & sear. Added unlit coal to remainder remainder of sns and set venom temp to 275.  I was surprised at how quickly my charcoal burned, about 3.75 hrs.  Just wondering if this is the norm.  I haven't used any kind of system like this before.  Debating wether or not to go ahead and buy the smoke fire pellet grill for longer cooks. TIA
 

[bigjeffb]

What kind of charcoal?
When I first got my Venom, I did multiple test runs using Kingsford Pro with my SnS, and got over 14 hours before I called it quits. Of course .I have a 22, and had it set at 250.