One thing I was suprised to see was the cross hatching from when I rebuilt it 30+ hours ago, figured it would have been long gone. I'd a thought it would have been totally worn in by now. Guess that's a benefit of running Royal Purple. I wonder if I will be around for .020 over?
The crosshatching is a matter of wear and the grit size of the hone used. The more the bore wears the less there is. I have seen crosshatching on engines that have well over 1000 hours on them.
The quality of oil has something to do with it.
Personally I don't like RP oil despite the fact they the brand has been around since the mid 80s. Royal Triton was another purple oil that was around in the 1960s.
Crosshatching is all but gone on modern automotive engines. The makers use a microhoning technique that all but eliminates break-in time. Since the honing is so fine, the crosshatching goes away quickly and the rings seat in seconds, not hours.
I have replaced rings on a couple of Onan engines and used a 600 grit hone. It took about one minute for the rings to seat.
The other factor is the type of cast iron that Onan used for their cylinders. A cheap cast will wear quickly. Onan was apparently very specific what cast iron was used. As a result, if you keep the oil changed, the engine will last a very long time as evidenced here.