I would say it depend... look at Julia Ann... i was la teen and was looking at some of her stuff... first movie i saw of her was called Veronica 2030 and i taped it on TV, so it must have not been too recent. And still today she is rocking it !!
Really depend on the mindset, the demand, the look and how she age etc. Sarah Vandella has been active since 2006 and peoples (me included) never get tired of her, cause she perform extremely well , is willing to do pretty much anything , so she always renew herself. She has not changed much physically since those years either.
Ryan Connor was out for a bunch of years and came back like a year or 2 ago and she is doing well.
But yeah its true Porn is a good bridge for escorts, they can jump there price from the average US price to 2000$ an hour, but the industry if played well can last as well. Last exemple... Capri Cavalli/Cavanni, she is super hot physically but has done boring 1 on 1 scene for most of her career wich lasted a decent ammount of years, then she started doing blowbang and interracial and it looked like finally she was going into hotter stuff and boom... she retired. I think its safe to say everybody would had love her to stay many more years and do more awesome stuff.
I think for a pornstar to suceed she must not give it all right away, play it well, add to her resume as the years pass by.
Nadia Nolimits, Lexei Bacci, Sheryl Ann...
Nadia Nolimits is pretty, but how much porn has she done? I saw her for the first time with Buno B then i searched for more of her and i think there was like 1 or 2 more scenes... Can't put every hot performers that done 1 scene of porn cause the list would be more than 10 names...
I tough of another one too that could had been on this list, Pamela Kane. She has been around for a while, done a lot especially in her early days. She seem to have catch an allergie to sperm a couple years ago sadly

but back in the days i remember her scenes from No cum dodging allowed and such, that was hot.