I change the oil, filter and plugs every year (and I only go 10-20 hours a year, max). These engines are basically abused from the minute the key turns on (high rpms before the engine is completely warmed up, high rpms for every minute the engine is running). Only thing between you and catastrophic engine failure is the oil! And it's amazing how fast these birds go through plugs. Any issues with drivability, first thing to change is always the plugs.