First, let's throw out the easy answer: you can hang on as long as you want to keep clutching the rope. After all, the increasing demand for rehabilitation counselors means you can write your own ticket, correct? Alas, all may not be as it seems. Let us explain.
Let's assume you work for a non-profit agency with dozens of active clients and only two rehab counselors. You're working a 10-hour day, trying to keep ahead of the mountain of government-mandated paperwork. You're steadily losing the battle, even though you're working through your dinner and TV time at night. One morning, your alarm goes off and you bury your head under the covers, unable to get on the hamster wheel again. Sounds like burnout to us.
However, let's not forget the other enemy that periodically rears its ugly head. If you work for a non-profit agency, your position may be partially (or completely) funded by grant monies. If you work for a state or local human services agency, your employment may depend on legislative appropriation of funds. In other words, external forces control the source of your paycheck. That's a risk you accept when you take the job. It's kind of like a game of roulette; you always wonder when your number will be up.