Odds of Hanging On
If you can hang with it and manage to land jobs, then you have a decent chance of making a career in cinematography. Many successful DPs perform their work well into old age. It can be very fulfilling, and doesn't necessarily grind you down like many jobs in the film industry.
The biggest trick to longevity is to make sure your style stays fresh and edgy—and that's no easy feat. The tastes of Hollywood and the movie-going public change rapidly. If you can't stay ahead of the curve, you'll be tossed out on your rump before the director says "Action!"