My Griz sander has had a bearing screaming for a couple of years, I have to wear ear muffs when I start it up, really loud but quietens down after the sander warms up.
I have changed this bearing out once before, a major job so I let it scream.
When I bought a new bearing the last time from Grizzly I bought some extras just in case. One day I will get motivated to replace the loud bearing, if I ever have any down time between projects.