For me anyway, to answer you better, it would help to know a little more about your warmer so people can make remarks to something similar they have used. There are many different kinds of handwarmers on the market. Some warm due to the fabric, chemical packs, battery packs, batteries, charcoal strips, windblock technology, metal in the lining, etc.

I have several sport muffs. The downside is that I don't normally need both hands in it at once, so I do wish for a muff that warms only 1 hand. I usually have one hand on the gun/bow or on the binoculars, while one is in the warmer.

Chemical warmers are sweet, but last too long, while I only really need them to last 3 1/2 to 4 hours, but for $1.09, they are still worth it.

Way too many questions left unanswered for me to comment much more. Can you give a little more details in which direction your warmers operate? Something. LOL!

iSnipe