Hi again.
For the heat, you can pick up a roll of the reflix (? )I think its called. The layered silver stuff at Home Depot or Lowes. Does a great job at keeping the heat out.
For winter, I would let the sun in whenever possible. When we are hooked up to power, we run electric heaters ( the tower laskos ) but that is with free electric. Are you on a meter there? Might make a difference. You will have to calculate.
For the a/c, I just take the pad out and wash it with mild soap every once in a while. Not sure if thats correct, but with ducted air, seems like it would be the same as a home a/c filter. Someone will correct me if Im wrong.
Probably wouldn't hurt to have the units checked. Doubt if it will be that much money. Maybe you can get your RV repair guy to throw in a freebie ;)
If you are feeling froggy, climb up on the roof and check it for rips, openings, exposed screws and cracks around all the pipes. Lap sealant and a caulk gun are your friends. Also check for tree sap... I think it can deteriorate (sp?) the roof if it is rubber.
Just be extra careful up there. No shame in being on your hands and knees ( one of the only times ) :B
Have a great week!
Cheryl