It depends....
I tuned up a China Girl to rev to 10,000 rpm and do 40mph.
I ran it all summer, mostly at about 25-35mph. Put over 1000 miles on it.
Would ride 25kms to work and 25kms back and then do 100 kms after supper.
Pretty much all WOT non-stop.
It got lots of cooling from the speed and I used a good quality oil.
I did have spark knock at times, but know it and backed off or found answers.
By the end of it my cylinder was quite wore, both rod bearings loose.
Finally a piston pin clip failed from fatigue, and scored the piston and cylinder.
Moral of the story. Speed kills, engines. RPM, compression and load caused wear and fatigue.
If I had run this motor at mild speeds, rpm and load it might still be running.