Most "modern" piston ring manufacturers that are "on the ball" (eg Hastings) suggest a break in of 10 x accelleration from 30-50 mph at full throttle.. that is all.
And contrary to popular belief, the bearings really dont need to be broken in at all.
But of course there are a million people that will disagree and fight it to the death and Im not going to take part in that! But thats what I say.
If its any support for the theory... I broke my last motor in, running mineral oil for 25kms while I drove it to the dyno.. low revs, high load, as recommended. Then dumped the oil, threw the synthetic in and gave it 3.5 hours of total abuse on the dyno. Compression is still sweet, oil usage is undetectable, blowby is bordering on absolutely nothing.