Racing is not going to significantly affect the thrust bearings. Racing does add significantly more wear to the main and big end bearings.
First of all you should check to make sure that they are in good condition. push the crank (pulley) back as far as you can. Put a dial indicator on the pulley and have someone depress the clutch. There will be a bit of motion but is should be quite small (I don't recall the spec offhand) keep in mind that the spec in the manual is for a freshly rebuilt engine so if you are slight over the bearing are still alright but check them every 10,000 miles or so.
Now to keep your thrust bearings in good shape
NEVER start the engine with your foot on the clutch. This puts full pressure on the bearings with NO oil.
Don't ride the clutch, hold it in at stop lights or whatever.
So:
1. put the gear in neutral, foot off the clutch and start the engine
2. shift gears, and put your left foot back on the FLOOR where it belongs
3. Stop, put car in neutral and put your left foot back on the floor.
The thrust bearings will last longer than the main bearings
Drive it like you just stole the car but keep your left foot on the floor as long as you aren't shift gears.