I have a Kawasaki FR730V engine on my lawn mower, which has an oil filter. Kawasaki says change the oil every 100 hours with no time limitation. They say that after the first 8 hours, you are to change the oil, which I did. I went with Quaker State Ultimate Durability for good protection and it was a good deal. Is it OK to let go till 100 hours even if it takes a couple of years? Even if Kawasaki didn't put a time limit on it, why do I see time limits on oil?