I've never been a fan of "cold therapy" like that, and now have a problem/condition that requires me to keep my hands warm or start losing fingers, but I've been reading a book on longevity and genetics and it turns out that being cold, rather than hot, for short periods of time is actually healthful and may lead to longer lifespans. The book is from a noted geneticist who is a Fellow at Harvard. I still don't see myself taking a plunge in a frozen lake though, longevity be damned!