Re: Bourns 6539/6639
I believe that the Mechanical Angle area says that models with stops at 340deg are available. There is also a Rotational Life listed as 10,000,000 shaft revolutions, which might help you to determine a property like max RPM. If you know your RPM at the shaft, you can calculate life expectancy.
Depending on the application, I would suggest using a rotary encoder instead of a potentiometer. We used this style of potentiometer on our swerve system, last year, to keep track of the angle of our wheel modules, and it worked great, but in that case, there was very little load on the pot's shaft, and it didn't have to rotate very much, very quickly. If you're looking for a high speed kind of thing, I think I would suggest looking into rotary encoders. Even the lower resolution encoders from DigiKey seem like they could be very useful. Say you have 8 inch diameter wheels (and you're using 1:1 ratio between wheel rotation and encoder rotation) and are using them with an encoder whose resolution is 32 ticks per rotation, that's approximately 1.3 ticks per inch, or 0.8 inches per tick.
Dunno, just a thought.