I just changed the oil in my Cub Cadet riding lawn mower. It hasn't been changed in 10-12 years of summer and winter abuse. It has lived a hard life. It fires on the first time and runs like a top till it's out of gas.
I drained the oil while it was 35*F in the shop... it took a while. It wasn't clumpy, it wasn't shiny, it wasn't any different looking than 6mo old oil. I didn't pull the valvecover or the head off of it, and I won't until she pops... but as it stands, my decade long maintenance intervals haven't let me down on the Linamar 14hp I've been running since the 1990s. This tractor runs for roughly 2 hours a week, every week, all year. This isn't typical for me with my other stuff... just one of those things I decided I would push the boundaries on and see how it went. I didn't think another 10 years were in the cards because the tractor is failing around the engine at this point.
Friend of mine just kept topping off the oil in his 90s ranger... went 90k before the body rotted off of the frame. From showroom new to the junkyard with the same oil filter.