Ummm, exactly 2 days, 4 hours and 17 minutes. That's if you're cooking walleye. If you're cooking smallies or trout then really only a day and a half. That's in the northern hemisphere. Reverse that if you are in Brazil, or, at altitude.
Of course, all of it depends on the size of the propane bottle, stove efficiency, length of cooking time and whether or not it's a full moon! :) I'm sorry, I've had a goofy week. Someone else can probably answer this question properly.