Odds of Hanging On
If you're still caddying when you're sixty, there are only two ways to explain it: you're Benjamin Button; or that vegan diet you swear by really does help you look and feel twenty years younger. Being a weekend caddy is a young person's game, and the ones who are older are only still in it because they're very good at the finer points.
Stay in shape, remain observant, and keep up to date with trends in the game. The physical aspects can take a toll on your body after a while, but you could caddie for a good long time if you reach the top levels.