It's like with any car, if respected and cared for it can go on indefinitely, rag the hell out of it from cold and don't bother getting it serviced then it won't last as long. Which basically means you have no idea who's done what with their car, even if they have FSH etc.
It's just luck of the draw really mate, find a decent one you like with relatively low mileage if I were you, then make sure everything's okay with it and you should do alright.
Good luck!
Darren