Yep, been there done that (and almost crashed).
I use a 12 race weekend limit for my front hubs, and then change them out.
Here's a tip, get a pair of uprights from a boneyard, clean them up and rebuild them with new hubs, bearings, and studs (I usually replace these as well since you have them apart and they aren't real expensive)
Replace the entire upright and then keep the old unit as an emergency spare. When it gets close to your service limit, rebuild your spare and then swap them out. It takes about 20min to change an upright but you need a bearing press to change hubs and bearings. You'll need to spot check your toe settings after changing uprights.
BTW, I wonder if anybody else has noticed the following:
In my last race before I changed my hubs, I noticed that the LF brake pads would get kicked back in between braking zones (I was at IRP which is one of the easiest tracks in the country on brakes since you only use the brakes 2-3 times a lap on opposite sides of the track) and I would have to pump up the brakes once or twice before the braking zone. Once pumped up, they worked just fine.
I'm suspecting that the bearing was starting to get sloppy even though the wheel nut was properly torqued, and the free play was causing the runout to increase and thereby cause the pads to kick back. I could not hear or feel any problem with the bearing, but at IRP you spend alot of time at 3 digit speeds and the track is pretty bumpy and it puts a great deal of load on the LF corner.
When I changed hubs, the problem went away.
Any thoughts on this being an early warning signal?
I have found the rear hubs to be much more forgiving, and they will get noisy when they start to go, and they don't seem to fail catastrophically like the fronts. But it's probably a good idea to change them on a regular basis as well.