2 hours into a brisket and...

First, this site is so unbelievable handy. I’ve got a long ways to go, but I would still being eating boiled ribs if it weren’t for you guys. (I knew better, but I didn’t know where to begin.) So, for all I’ve learned and all I expect to keep learning from the fine folks that use this site…THANK YOU.

Anyway, I've completely changed up how I'm doing things. I had been burning only cherry wood up to this point, and I mean only cherry wood. No other fuel. But the more I have read here, the more i realized I am probably in the minority. And it probably explains why I have to pay constant attention to my fire and I get temp fluctuations that range from 175 degrees to 450 degrees. It wasn’t working for me. (In case you couldn’t tell, I’m relatively new at this.) So I have been back at reading/studying this forum and here's what I've got going on:

• A small brisket (about 8 pounds, but oddly includes the flat and the point)
• An offset smoker (Brinkmann)
• Made a coal basket using concrete lathe (about 9 inches in all directions)
• Filled the basket about 7 inches high with Kingsford Original and dropped 12 lit coals into the center (minion method)
• Included about 9 pieces of cherry interspersed into the briquettes, each piece being about a cubic inch

So no I am 2 hours into the process and I’m concerned about the longevity of my fire. This is my first attempt using this method and was mostly concerned about being able to get the temp up high enough. No problem there. Rock solid 245 degrees the entire time. Almost, anyway. The temp spiked very early until I closed up the air inlet. Currently, the air inlet is closed completely. The chimney is wide open. I have a water pan with maybe a help gallon of water on the fire side of the meat.

Here’s my concern. Within 30 minutes of dropping the lit coals into the basket the entire pile was lit. My understanding was that the pile would light gradually over the course of a few hours and provide me with steady heat source that would last (hopefully) at least 8 hours. Now I’m not sure it’s going to last four hours.

Should I just relax, or do I have a problem?

So, if I can control the unwanted air from getting into the firebox, I can extend the amount of time I can get from a basket full of coal? Makes sense. I've read up on the various mods for my type of cooker, which I wish I read beforehand. I would have bought a different type of cooker. I've seen a few custom ones on here that I really like.

Glad to know that adding fuel is the remedy because I couldn't think of anything. But, I was hoping it was the shape of my basket or something simple like that.