I'd say those time limits, like three months, are just because the oil companies want us to buy more oil. You car manual does not specify time limits for oil either. Just mileage. I would say the truth is that oil breaks down through use, not time. I would not leave it in there forever, though. If you do your own maintainance, then the costs are reasonable, if you use non-motorcycle specific oils. Special motorcycle oils, I have determined, are a bunch of crap. Apparently, so is "synthetic" oil. Nearly all of the synthetics available now are not manmade oil, just highly refined dead dinosaurs. Shell car synthetic is still man-made base, but not the Rotella Synthetic. Weird, I know. In any event, if you don't ride that much, I would change the oil at the end of your actice riding period, to get the gunk (that's acid, and soot) out of the motor before you shove it in the garage for the winter. If you keep riding all year, as I plan to, in Florida, then I would say every three months is reasonable. Depends on local conditions, and the rider. Hot dog + dusty conditions= more changes. Easy going + easy conditions=fewer changes. Your mileage may vary. LOL That was kinda funny. CB