I have a Barley Crusher. Like others, after while (~1,000 pounds of malt in my case) the idler roller stops turning because the knurling on the rollers is worn and won't consistently grab the malt. To the manuf's credit, it does have a life time warranty and they did take it back, replace the rollers and return it to me. It takes about 4 weeks from the time you ship it until you get it back.
I'm guessing that the same problem will reoccur after I put another 1,000 pounds through the mill. For me that will be about 3 years from now.
At that point I don't know if I'll get it rebuilt again or just replace it with something else. Cross that bridge when I get there.