actually it probably depends on what protection it has. I know on my motherboard I can choose between 60, 65, and 70C for the max point of the CPU temperature. after that it shuts it off.. On real hot days (not summer) I've had it up to 55-60 so it's reaching that point but it will be alright..
and why do you want to keep it on all the time? that doesn't make any sense