Good points. I can understand the buildup in the pan, that's a great point about the fins. However, I have run this engine with the valve cover removed and oil quickly gets everywhere even at idle. I would think there should be plenty of heat and oil flow/splash in the cylinder head area to prevent any real buildup?
I have worked on other engines with much more mileage and an unknown maintenance/usage history that had a cleaner head and valvetrain than mine with about 40K miles since the refresh, easy usage, and <5K mile oil changes.
My friend's almost 200K mile Cadillac CTS is a great example of this. When I changed the valve cover gaskets and replaced the cracked oil pan, that engine was pretty darn clean inside. The oil pan was definitely cleaner than mine and the head and valvetrain was somewhat cleaner than mine too. He owned it for about 2 years and did 6-7K mile oil changes with whatever synthetic was available cheapest (usually STP or a generic parts store brand), but the rest is unknown. It's totally possible things about other engines are just better for staying clean than mine, I just wonder how much the oil contributed to the buildup. Sounds like in my case the design of the engine has more to do with it than anything else.