This same question was on here a month or so ago. Thermacells work wonderful if there's nota lot ofwind. They can be used multiple times if the pad still has color. Keep a small ziplock to put the pad in after it cools off. The butane cartridge is good as long as you can see the fluid in it. Keep an extra refill with you just in case. Whomever came up with it deserves to be a multi-millionare!