Reading through many of the threads on here, I constantly read about break in oils, synthetics, etc. Some manufactures recommend brand "X" over brand "Y" or"X" amount of gallons of fuel on petroleum based oils, then switch to synthetic for proper seating of the rings. blah blah blah

We've all read these threads!

My questions is how do you know when the rings are properly seated?? When is the magic time to switch??
(and please don't say because engine manufacturer "A" says 2 gallons of petroleum base oil, then synthetic or manufacturer "B" says 10 hours on petroleum, etc)

I'm more curious as to a physical, or visual test one can do to ensure that his engine is breaking in as it should.

thanks
Sam