Barring some sort of tragedy like Jimmy's, we'll all grow old and die. We'll all make poor decisions in our personal lives or careers. Assuming that we take chances and try new things rather than stagnating, there will always be failures. Even though Dean told Roy Schatt that he didn't expect to live past 30, that doesn't mean he didn't want to. I've said the same thing, and it was more a statement of my own expectations than what I actually wanted out of life. But then the question becomes, is it better to live a short life and die before you ever have the opportunity to fail spectacularly?
The answer is no, and it should always be no, and the fact that some people think it's actually yes shows that our fucked up enshrinement of youth has reached a new peak of cynicism and tastelessness. If Dean had not died young, would he have ended up as a mythic cultural icon the way he is today? Probably not. Would he have been given a chance to do more, be more, settle some of his demons, and find someone to love long-term? Yes. And maybe culture would have had to find another icon. So be it, I say. I'd know I'd prefer that he'd gotten a chance to live his life rather than burning out too quickly and being enshrined in some sort of legacy that, more often than not, misrepresents him.
Yeah, it sure is great that he died young. Jesus. Don't be assholes, people.