ORIGINAL: blw
I wouldn't hesitate inspecting bearings as soon as they felt gritty, ran hot, made noise, or had excessive play. The potential for a lot of damage is too high to procrastinate, IMO. OS parts like liners and pistons are extremely expensive.
So true.
A guy turned up at our field with *three* engines that all had bad bearings. He'd used CoolPower for less than a month and they'd all rusted badly -- go figure.
It took me about 15 minutes to change the bearings in one of his engine so he could fly.
Fifteen minutes of time and $7 worth of materials is a small price to pay to ensure an engine isn't ruined in the blink of an eye.