I change oil every 3,000 to 4,000 miles on all my vehicles and I run full synthetic in all of them. It isn't the oil that breaks down at that stage but it is the additives that do break down around that stage. That is why the need to make the change. With bikes the spring oil change is to get the moisture out that has built up as well as any acidity and heavy metals from chemical reactions.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!