I've ran in the winter with my MMM for a couple years now, ever since they came out. Last year I coated my esc with liquid tape because I was planning on a lot of water. I never had a problem with any of them. Check out this video and you'll see what I did with my two week old Flux.
http://www.youtube.com/watch?v=lLv_rCtme0M
Still works fine!
RC-Monster RC8T 1515 2.5D/MMM/5s RC-M 4500mah
SC10 MMPro 13.5T 2s NeuEnery 5000mah
RC18T Mamba 25/5400kv 2s lipo + 6s NiMh