I think a lot depends on what you're "running in",
a tight engine will generate more heat than a worn
example which can close up tolerances. I would say
take it easy on rpm but avoid laboring the motor
as that really drives up the heat at the top end.
Racers tend to go for the thrash to avoid glazing
the bore & wear is a generally secondary issue to
them. Bear in mind a race engine will require a
rebuild far more often than your pride & joy should.

Cheers Legion.