When I worked parts we had a eng supplier who set break in standards for their motors....
from a rolling start ( at temperature) in low gear run it up to 50 mph for I dont remember the amout of time, 3 times. Let her cool down change the oil and off you go...no lie.
also anyone who has ever built race engines. other then the 20 min break in for the cam has anyone ever easily broke the motor in?No..A few laps at half throttle maybe and cool downs before the actual race or hot laps but thats it. Ive never babied a motor either and never had one break because of it.
If a new motor is going to break its going to on the short term....