Make sure you're fitting them correctly. Don't fit them as per the previous set and assume they were right. Check with the manual as it is quite easy to fit them incorrectly. There's a chamfer on one corner. Also, check the condition of the reed cage. It's possible that the reeds don't seat correctly due to a problem with the cage.

Changed on mileage, I've never had a problem with standard reeds. In fact, I'd heard that carbon reeds can be problematic.

I try to stick to 12500rpm but off the line it's easy to exceed this and on occaisions, I've seen just short of 14000rpm. Down changes I keep well below 12500. Closed throttle, no fuel, high revs etc etc.
_________________
If it ain't broke, fix it until it is.