I have a large 250 gallon tank smoker that is wood and gas. I have to do some mods on the wood part because it doesn't get to temp with just wood. The gas element in the cooking champer is 60 inchs long and has about 2 inch slits cut into it all the way down the pipe. I can get it up to 400 degrees with just the gas but, I want to cook at around 250-275 degrees. My questions is this. How long will a standard propane tank last at 250-275 degrees? I have 6 butts to cook and i will be useing some cherry wood also to give it flavor and smoke. I just have a standard propane bottle that one would use on a backyard grill. Thanks.