[grumpyunk]

tknj99.... I think it depends on the kind of riding. I would have no problem using a 1k interval, given a mix of traffic, highway and off road or trail usage. If you can keep a sort of mental counter, not too specific, but a general "I think I rode a lot going real slow this month", or "most was hignway" or about a 50:50, etc. If you feel you did a lot of riding where the engine was not getting cooled by air moving over the fins, cut it short. If OTOH, you did a lot where there was a good breeze, keeping temps within a reasonable range, ride some more.
I used(still do) pull the dipstick, and take a whiff of how the lube smells. Maybe I'm nuts, but think I can smell oil that has had enough and is ready to be drained & refilled. If it still smells 'good', like it did coming out of the jug, it is likely still good. If it smells 'sour', then it is likely time.
If you stick to a 1k interval, come snow or sandstorm, these engines will be fine. It is not that exacting a design, and doesn't really care. The crankshaft runs in ball bearings, the cam on a bushing that gets drooled on from the rocker arm area, and the cam/crank gears are also gravity lubed. Rocker arms and pushrods have a feed via the rocker arm cover, with drilled passages to drool lube onto the 'right' spots.
As long as there's lube, it should be happy, and doing changes early or late are not critical for longevity. To repeat, it was designed to be poorly maintained, with lubes that are on the level of what you would by at a dollar store, with a 'funny name'.
It does feel generous to baby them, though.
tom