I've done the old PC recommended 10x full throttle accelerations from 30-60mph, and as a result none of my rebuilt engines ever used any oil. I would still do it today if I rebuilt another engine, because it's a good idea. Run engine around 2000RPM for the first half hour (after checking oil pressure, coolant etc) to break in the cam, then go on the road to do the rings. That's how I was taught.

1965 C60 school bus | 1967 GMC 6500 school bus