That is very interesting.
I drained my oil because I am due any way, and it just gushed out like water. Actually gas and oil mixed. Lots of gas. The thing is, I'm not sure when this has happened or if it just happened slowly over time. Unlike you, I do not check my oil that often. But I don't ride very much either. Usually just around the yard doing small chores or over to the neighbors. My choke pull is right on the carb. but is the same type with a centering pin and a rubber seal. Maybe this is where my problem is. I will definitely tear this down and check it out.