Typical porn career is two to three years. A few stars are into it, most are not and will escape it for greener pastures once they can afford to.

Obviously some stars do like it, or aspects of it. So long as a star is in demand, the money is much better than mainstream film acting. (Most film actors can't make a career of their gains, even under SAG).

Its noted that Ron Jeremy is far more proud of his mainstream bit parts than all his porn, but a single scene is worth all of them put together.