GD, I don't know your customers, how their cars are set up, or if they're actually any good at driving or not. It really doesn't matter how many sets of rubber they have, or what kind of cars they compete against, or anything else really.
First off, I'm talking about the 5x100 wheel bearings only. 5x114.3-equipped STIs got different, stronger wheel bearings.
Our WRX is a daily-driven car that, early in it's life, was used as an Auto-X toy by my father and I. Two drivers per event, 6-10 laps per driver, 6-10 events per year for 5+ years. The original wheel bearings started to fail around 120k miles. One failed radially, one failed axially. Stock suspension, wheels and brakes (SCCA D-stock rules), but with the stickiest summer tires we could afford.
When I looked into replacement bearing options I did a ton of research. I suggest you do a google/NASIOC search for a guy called Gary Sheehan. He was the driver who debuted the WRX in the USTCC back in 2002/2003. His front wheel bearings were dying due to excessive brake heat conducting into the hubs, the bearings and was cooking the grease until the bearing physically failed. The fix was multi-faceted, but essentially what the team did was:
- 2-piece brake rotors (Stoptech BBK, said this was the #1 thing to preserve bearing life)
- An older bearing part number that is now NLA, which had 8,000 lbs. more load capacity vs. the OEM bearing
- Repack the new bearings with a nylon-cage-compatible, high-temp grease (DuPont Krytox, NEO HP800, etc.)
- Over-torque the axle nut to 145 lb-ft. (As recommended to Sheehan's team by the lead tech at SOA)
Gary believes the bearing package is the weak point. Heck, the conversation even drew in an engineer from NTN who gave us input for the alternate bearing part number and also advised on the proper grease to use that won't degrade the nylon bearing cage.
TL;DR - The 5x100 bearings DO have premature failures if in "extreme use" cases.