It must be incredibly tough being a male porn star and I very much doubt I would be even near to being up to the job. I do bear this in mind when I (occasionally) criticise male porn stars for their performance, however it does annoy me when their shortcomings are needless and self-inflicted, such as throat-grabbing, generally treating girls badly etc. I feel I reserve the right to criticise those but yeah, you have to take your hat off to them in terms of how long they perform in any given scene, for sure.
I suppose it's this difficulty level that allows them to have such long careers, which can in some ways be detrimental to viewers as I feel it's important to see new male performers from time to time. Whilst I wouldn't expect directors to treat the guys exactly the same as the girls in terms of turnover ratios (and I'm happy for them to have their own small "core" of guys up to a point), I would like to see them promote new male talent a fair bit more. There should always at any given time be a good bunch of guys in their 20s doing the rounds for me.