Well we have only had ours a few weeks (284BH) but the original owners had it on a permanent site every summer, indoors for winters, but never cleaned the roof. So I'm going to go the Dawn route and see how that work.
I have a30X80 shop for winter months and if the Dawn doesn't get it done once I put it away for the winter I will get a little more aggressive. Also the seals around the slide are moldy so I will get after them too.
Otherwise the trailer for a 2013 is in great shape, all the graphics are good....just a coat of wax over the winter and good to go.
We did upgrade the front TV to a 32" -- the previous owners had removed the rear dinette and installed a permanent bunk there.
A nice upgrade from our little '94 28' Prowler