See, you see Preston as not being a very good actress, while I see her as a good actress who has never picked a great movie to show us how much talent she truly has.  If things continue as they have been, we'll never know.  In either case, though, the result is the same - her career will only last so long, as you put it.

Well, Meryl Streep seems to keep getting good roles, and Angelina Jolie and Sandra Bullock, both of whom seem to get stuck in the same rut Preston has always been stuck in, still turn in the occasional knockout performance, something Preston has yet to do.  Shall we talk about Judi Dench or Helen Mirren?  I'm not saying age isn't still a problem with actresses landing roles, but it's much less of a problem now than it ever has been.  Now, let's look at Kate Winslet, who is at least 12 years younger and has made a career out of knockout performances, one after another.  Preston has yet to do that once, yet she has the talent.  There's no excuse when you have the talent but you never landed the right movies even once in your career.