Our experience:
-I wouldn't mind having the topper as when the times we park under a tree, I do worry about us having leaves, etc on the top of the slide. As of yet we haven't had to clean anything off, but I don't always rememember to check before bringing the slide in. (Maybe we should add that to our check list when leaving the campground!). Anyway, it could be a nice addition.
-From what we learned at other forums, the consensus is NOT to buy the warranty for a tt. Jayco has the two year warranty and supposedly anything major that can fail (that we aren't responsible for happening) would probably do so within that time. Just be good about checking/cleaning roof once a year, etc etc etc). We opted not to buy the warranty. BTW, some research on line may help you find possibly the same warranty as your dealer for about $1000. Dealers like to add huge markups.
-Once again, consensus with aluminum siding at other forums and from respected dealers.... just wax once a year. We paid a guy $125 to wash and wax our tt back in November. He was one of these mobile wash guys at a campground we went to who you could ****er around with the price.
Of course, that was just our experience...