We used stock single valve springs to do the run-in on every race cam we installed, to keep the pressure of the triple spring setup off the new cam. After a 20-30 minute run-in on the dyno with the stock springs, we would pull the heads and install the heavy pressure springs. Of course, those engines were producing 700+ HP and turning 7K+ RPM. They were totally worn out in less than 1,000 miles around a 1/2 mile asphalt oval.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!