You could be getting lucky. Still, I'd heartily recommend that you frequently inspect your spark plug tips using a magnifying glass, looking for "shiny specks" until you're sure you're not having problems. There is such a thing as detonation that isn't pronounced enough for you to hear as knocks, but can still chew up your piston tops (where the shiny specks come from) over time.
I think you may have meant hardened valve seats, not guides, yes?
It's pretty unusual for someone to be able to run at 10:1 with iron heads and pump gas without having problems.