I think my Briggs and Stratton has lasted so long without oil changes because the motor doesn't really "work" that much. By that I mean I just set the RPM high enough to cut the grass and leave it there. Thinking back, we used to give 25 gal drums of used motor oil to guys running saw mills, open boat fishermen, guys running small power plants etc. and considered that good business for gas & diesel sales. Most of those motors were also low compression with not much change in the RPMs so used oil worked fine in them. A lot of our bikes today have high compression tight tolerance multi cylinder performance motors. What I haven't seen mentioned above is that some folks like to lug around in high gear and not "over rev" their motors, while others like to ride hard and keep their bikes in the power band. From my experience differences in riding style effects oil life. Personally I take the suggested kms between oil changes as literally a "suggestion" and keep an eye on the sight glass or dip stick and the smell and colour of the oil. The number of cylinders and the cooling system seems to make a difference as well. For example I can run the K13GT hard all day long on multi day rides the oil stands up way better than if I run my R12GS the same way. I guess the difference in HP, cooling and number of cylinders allows the four cylinder liquid cooled motor to demand less of the oil than the air/oil cooled twin given similar performance requirements (for example two up loaded freeway touring). So while I appreciate the advances in oil and motor technology I always keep an eye on the oil as riding conditions may vary. Same for transmission and final drive however the differences are less noticeable.