foggytown says...

I see it recommended all the time - sand with low grits to shape then
220 grit for finish. But why stop at 220? I have used 320 (even
thinking of trying 400!) on a ROS to sand surface areas to an almost
glassy smoothness and I feel that I get a better final finish because
of it. At least I THINK I do! So far I've only used clear gloss
polyurethane and it's almost like a piano finish. I haven't been doing
it long enough to know if there will be problems over the years. Maybe
it's too smooth? Anyone have any ideas?

FoggyTown

I stop at 150, usually worn out 150. No matter how much you sand the
wood, you will still need to sand the finish coats. That is where the
action is as far as I'm concerned.