They always look good until you pull them out, wash out the grease, and feel how rough the bearing is.
My sleds both had roughly 6500 miles each and I had greased them every year. They looked clean, but I was replacing the drive shaft on my Attack and checked the bearing whilst it was out. I'm glad I did. I pulled the bearing from my Apex and it was much the same.
I'm sure they would have continued on fine, but for $20, from now on I'm thinking of replacing them at 5K intervals.
I did check my friends 2012 sled with the plastic cover and his looked great at 1500 miles. I'm thinking of adding the plastic cover to my sleds.
Does anyone know if you have to remove the drive shaft to install these?