I'm sure you will put it to use anyways. I picked up a JR3 press a few years ago for about $40.00 if I remember correctly. Haven't got it mounted to the bench but I will keep it around just because.
Not sure about the RCBS press but the Lee's one can get replacement linkage parts for them but again as cheap as used Challenger presses are if it wore out or broke I'd just toss and replace with another used one. Especially if all you are doing is seating and crimping, not much force or leverage needed there.