As not surprising, a lot of replacement parts for ANYthing these days are sub-standard in quality and useful life.My first pair weren't replaced until 2006 and my A806 was built 1978.
Replacements have started to squeal at about 6-7 years and lost spin speed.
Reviews show a few pissed off sellers.
Just make sure the spring loaded sliding motor mount isn't binding.The main drive belt is glazed a bit, no oil from trans or brake is visible. Squealing wasn't uncommon with aftermarket belts from my experience.