The valves actually don't care, all that the break in period is for is breaking in the cam lobes and the lifters... because they are new they have to rub on each other a bit to get their initial wear patterns in so I can vary the RPMs without causing damage. There is special moly grease used, and while it sounds simple the monitoring that is done is quite extensive. At least the way I do it. Usually I run engines on the stand at lower RPMs for about the same amount of time, however the cam grinder made it very clear, he wouldn't warranty the cam unless I blasted 2.2K rpms for 30 minutes, so of course I did.
So, now the engine assembly and testing is done. Next is to work the rest of the kinks out of the turbocharging system.