Going off to the 9 hour enduro, I'm thinking about changing my wheel bearings, but I understand the rears are a pain. My chassis have 230K on it. No play, but I wonder if it's worth the effort to get them done for durability reasons?

If it were me, I would do them - especially if they've not been replaced since building the car. 9 hours is the track time equivalent of roughly 4 weekends, all at once, with lots of time for things to get hot and load up. I've never driven Road Atlanta, but it seems like all of those high speed, high-G corners could be tough on wheel bearings, and I'm not sure I've ever seen a spin/crash video from there that didn't end up with a lot of body damage.

It's a fairly big job to do the rears, but each individual step is pretty straight-forward. I've never done it on a late car, but on an early car the two worst parts are loosening the axle nut (350 lb/ft if I remember that right), and removing/reinstalling the outboard end of the half shaft (if you do it right, you don't need to remove the inboard end...just make sure you have a plastic bag handy to cover the outboard end when you take it off so that you don't get grease everywhere.) Also, it's a much easier job if you have someone to help.

After more checking,, one side was definitely tighter than the other - so they are being rebuilt.

This is what I found while getting ready for Daytona this year on the rears.

Well, can't get it to upload but it was nasty, inner bearing was intact but three separate pieces cracked completely through.

Car had 160,000 miles on chassis.