I do not believe that breeding takes much of a toll on the male minus the supplying the sperm part and that is replaced very soon after. I'd say as long as your male still wants to breed and is physically able let him. If someone who has had panthers that are older than 3 years, like my oldest male at the moment is, I would really like to hear an experts answer one this one as well. Like I said my oldest at the moment is just shy of 3 years and he is still a verocious breeder.