I had a Hayward motor that lasted about 6 years, running year-round with no problems--I don't know how much it would have cost to replace just the bearings, but the guy that came to fix it replaced it with an A.O Smith motor for about $200 and I've not had a problem since....

I don't think chems are the problem, I've been using BBB with some trichlor for 8 years now and haven't had any other motor problems. I do have to replace the motor on my koi pond about once every 2 years, though, and that's with no chems!

Janet