Yep, FWIW I totally agree. Nobody is lying when they point out the durability of synthetic base oils but there is an additives package involved in oil engineering too, and contaminants naturally build over time. The "package" doesn't generally share a synthetic oil's special construction and key components of it get depleted, not simply as a function of time, but also as an immeasurable function of the things your air cooled engine can put the oil through. Air cooled motorcycle engines are a brutal environment for oils owing to, among other things randomly high and varying temperatures.

Anyhow, after what for me seemed like a lot of research on the topic , I've gone to synthetic oils for the benefits they give while retaining the standard change interval. I find the economy of justifying the switch to a clearly superior product by attempting to wring the extended life out of it a bit self deceiving anyway, (you get what you pay for period). Also, there is absolutely noting that will ensure an oil's continued containment free integrity like frequent changes. If you can't afford synthetics, not using em is ok IMHO, but extended change intervals in an air cooled engine is not something I can pursue in confidence. Just my $0.02.