I wouldn't have thought there was a service life on valves unless the engine is living on the rev limiter all the time. I've never heard of a 916 dropping a valve either. Just a light grind in would be enough for another 30,000 miles. Don't forget that desmo valves are not smacked back onto the seat by a spring, they are mechanically closed so they should be less stressed than regular valves.
My ST4 has done 24,500 miles and the compression is still fine. I started it today after a gap of nearly four months and it fired after two turns of the engine.
Thats my thoughts anyhow!
19-Feb-2006, 22:21 
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