[tbirdtbird]

For the benefit of those readers who dig up this thread later on, I'm with #5, ie I would never break in new rings on synthetic oil, it might take a long time.
The idea of break in is to get a lot of wear quickly to get the surfaces that rub each other to mate. Once that is done, your compression goes up, your volumetric efficiency (which is a dynamic measurement, not static like CR) goes up, you'll have less blowby, less oil contamination, etc. Once this happens the wear reduces significantly and now longevity kicks in, if the break in was done properly. Then you can switch to synthetic if you want. But honestly it is not needed and costs more. Changing the oil is way more important.

This is all very different with modern cars because in moderns the tolerances are way tighter, and the metallurgy of all the parts is different. Do not make the mistake of comparing a modern engine to an A motor