Drag racers rebuild their motors often enough they don't care about rings seating or frying a clutch by hazing it before it's been broke in. I believe a solid 500-1000 miles, atleast one
oil change allows for proper break-in and engine gunk to be flushed. But hey, each camp has their opinion...yet, I've never heard an engine builder claim harm by breaking in a motor w/ milage...but many warn against flogging it early in it's life.