You put $10 + dollar a quart oil into your lawn mower?
Don't get me wrong, I preach small engine maintaince more than most people I know..... I change the oil in my riding mower every 50 hours (right now it has royal purple 10W-30 synthetic that I got on clearance for $1.50 a quart and my tractor holds the better part of 2 quarts) and I STILL think this was a bit crazy.
It's nice to see the UOA, but unless your getting them for $10 or less it's a serious waste of money. I'd be dumping the oil and replacing it every spring. I don't bother with synthetic in my push mower, I just put a fresh fill of 10w-30 in each spring, clean the air filter up twice a season, and make sure to always run fresh fuel through it. At the end of each season I run the last fill of that "tru fuel" or pre canned fuel you get at wal-mart or whatever in it... no ethanol.
I can get on board with yearly oil changes. Amsoil brand oil and UOA's on a push mower... way overkill on a splash lube setup.