Huh, I ain't no spring chicken and I do most of my own work. have never had a problem with Seattle Cycle on the occasions I've had 'em do stuff. Usually tires, but once in a while something else.
Far as warranty issues. Not a thing for maintenance; although recording that ya checked 'em, mileage and the date somewhere ain't a bad idea in case someone asks.
I did have the exhaust valve tighten up on my old S200 once over about 6k miles, same basic motor I believe. It doesn't hurt to take a look now and again, but sounds like you've been doing this a while so you know the signs to watch for.
I knew that the valve clearance would not need adjustment , But I went through the motions anyhow and sure enough the clearance was right on at 004. The book said to have the shop do it. But I am 100 miles from the shop. And have been doing valve clearance check/adj since 1950. Shop not doing it might raise some warranty Q's. But who needs them. Besides, Seattle Scooter Center has a jerk working there that gets his kicks screwing over Senior citizens.