Odds of Hanging On
You're not going to be booted out because you got too old for the job. You're not working in construction or professional sports. There's no reason any body part should be giving out on you; and if you start having trouble lifting the jar of exfoliating scrub, you have problems way bigger than whether or not you have a job tomorrow.
That said, if you want to ensure you stay in the game, keep your skills sharp and stay on top of the Internet-induced trend towards mobile facials and mini-sessions. Keep it fast and tech-oriented, and you'll keep your clients.