Both of my Thumler's UV-18's are over 35 years old. I've replaced the motors in each of them once in that time, and they're still going strong. I have no idea how old my UV-45 tumbler is, but I know I'm at least the third owner of this beast. It's industrial grade and everything on it is heavy duty.
I think at four years your UV-10 will just be hitting it's stride. Thumler's knows how to make tumblers that last, and they're nice people to deal with, too.
Hope this helps.
Fred