I rely heavily on heat and cold exposure as part of my broader lifestyle regimen. Heat comes in the form of sauna time, ideally at least 3 days each week. Cold comes from cold showers, cold baths, and swimming in Lake Champlain throughout the colder months. I live in Northern Vermont, so the lake gets cold and sometimes freezes over. Not unusual for me to bathe in water that is just over 32 degrees Fahrenheit (0 degrees Centigrade).
I do not think either heat or cold exposure ages you. I suspect the opposite is the case. Both can trigger the release of biochemicals that reduce inflammation, and anything that reduces inflammation helps us age more gracefully. Beyond that, I have been doing heat and cold exposure for over a decade now, and most people mistake me for being about a decade younger than I actually am. (I am 43, and when I meet people it is common for them to assume I am 30, sometimes even in my late 20s).