Had high hopes for these insoles to allow me to ride my fat bike in comfort using my 'California Winter' cycling shoes and not having to wear regular winter boots... however I never got the sense that the combination of my waterproof shoes and these insoles were the right choices. While I never put the insoles in the freezer to check if they were working, I believe they were working as advertised, but being active in non breathable footwear caused a lot of sweat and chilled my feet which the insoles could not overcome. I also tried these in other winter shoes and I got better results in bigger looser boots. The battery seemed to work for the advertised time. Overall the insoles worked as advertised, but you need to make sure that you've got room in the boots for their extra bulk since they are a good deal thicker than any regular insole or orthotic inserts, AND you need to keep your feet dry because they just don't have the heating capacity to overcome damp feet and socks.