My 92 FZR1000 made it to 30,000 miles before one of center intake valves recessed so far that I couldn't get a thin enough shim to set it right. I checked it every 6,000 miles.
The exhausts never changed in that mileage but the intakes and particularly the center ones kept getting tighter.
For sale,2 SR500's, Virago700, VFR750, VTR250... Not for sale RD350B RZ350 and XR400R. Looking for 250ec Gas Gas