I just tore apart my buddies engine that had N1 cams on stock springs and retainers for over 2 years with no rev limiter reving to 9k because it still made over 180whp at 9k. gears set to +5,-5. Motor saw probably 11-12k several times during mis shifts with no rev limiter trying to quick shift into 2nd. Never had an issue. There was no signs of piston to valve contact when I tore it apart. Valvetrain all looked perfect. The n1 cams are definitely a very very smooth ramping cam.