So somewhere in another forum on here I read an old post about saving and re-using chem warmers. It simply stated that if you say, spend 3 hours plowing the driveway there is a lot of use left in an 8 hour warmer, just seal them in a plastic bag. Sure enough, this actually works! I just put them in a ziploc baggie and in a few they use up all the oxygen and stop producing heat. When you take them out they re-activate. Could believe this actually works and I though I would share since everyone is having to pinch pennies now a days.