Odds of Hanging On
If you can hang with it and manage to land jobs, then on a personal level you have a decent chance of sticking to it. Many successful DPs perform their work well into old age. It can be very fulfilling and doesn't grind you down like many jobs in the film industry. The average DP works for decades longer than the average Director.
The biggest trick to longevity is to make sure that your style stays fresh and edgy. No easy feat. The tastes of Hollywood and the movie-going public changes rapidly. If you can't stay ahead of the curve, you’ll be tossed out on your rump before you can say "Action."