Bugbite,
The best I've gotten is 15.1 solo on the highway. City is about 9-13, depending on terrain and your foot. Towing is about 6 for a heavy trailer, 8-9 for an average size. Those figures are for the gasser V10. Diesel however can get upwards of 21 Hwy (solo) if it's equipped with proper aftermarket stuff. Stock, the 7.3L get about 17-18 Hwy, 13-15 city, and about 13 towing on the highway. The city # drops a lot in the middle of winter with cold starts, etc, which do suck up fuel. A very cold, bad day would be about 11-12. I've heard that the '03-'07 6.0L can get better mileage (maybe mid-20's), but I can't confirm that.
I haven't left the Sunline family totally. After all, I do sleep in one every night (see post called "The secret is out..." in Sunline community), but I am currently looking for another Sunline. I don't have any RV at the moment. My parents however do have a Fleetwood MH and Weekend Warrior toy hauler.
I don't see any reason why you wouldn't get a warranty on the roofs. The roof material is made by a separate company and should be warrantied by them. If it wasn't, I'd be surprised. The old roofs used to carry a 10 year warranty, but the company has now upgraded to a 12 year because the product is a little more devoloped and has improved some over the years. I don't think they would lessen the amount of time. The only thing is, if you have a problem down the road from a seam leaking, and it does damage to the sidewalls, that is a manufacturer/installer problem, not the roof manufacturers' problem. So, you would have to pay out-of-pocket to fix that part. The roof warranty itself should only cover the roof tearing, cracking, or leaking in some place not in the seams. Depending on the dealer you buy it from, if the roof leaked at a seam within the first year or so, it may be included if the dealer gave you a tongue-to-bumper warranty on the whole coach.
Jon