I just got back from doing some hikes at The Buffalo National River. The first night got down to 20* and the second night was about 24*. I had my 5oz Climashield XP Top and Under Quilts, as well as my windshield heat reflector. I believe that Jeff has talked about boiling water and pouring it into a Nalgene to use as a hot water bottle. I decided to try this the second night and WOW, THIS WORKS GREAT!!!!!!!!!!!!!!!! I usually have a problem getting my toes to warm up, but not with this. It instantly warmed up my quilts and was still warm 8 hours later that morning. I do not care if I have to carry another fuel canister just to have to do this, this is awesome, and I'm sure that you could extend the range of a bag/quilt by doing this. Just thought I would post this for all yall that are thinking of ways to stay warm, this is very easy and takes no time to do at all. I hope it helps yall out.