Hello, Longtime BBQ'er...New to this Forum...New to Smokin'. I have wanted to do some smoking for a long time. I'm now ready to do so. I have a good Weber Gas grill I'll start with. Bought 2 cast iron smoker boxes. Also, just bought & received the new Maverick ET-732 dual probe thermometer. My question I know depends on a few variables but basically having the internal temp at between 225-250 degrees F, how long should I expect a full propane tank to last? Thank you for your help.