NEVER use the cheap tape rewinders. They are cheap for a good reason. They do not slow down at the end of the tape, they just hope that your tape won't break from the hub when it hits the end of the rewind at full-speed.
Seriously, don't worry about wearing out the camera. If you use the camera to make money, then you should hope that you have enough business to wear them out.
The same goes for "wearing out the heads" from using the camera as a deck. Most of us who use our cameras to generate income would welcome the business volume that it would take to wear out a camera from normal use.