Do you use slide supports?
How do you maintain the rubber seals?
There are all kinds of products for rubber seals - and there are pros and cons to using them. You should be good for the first year and I would call Kermit and ask his advice.
Do you add insulation to the underside?
We do not use any insulation and have never found a need for it. We notice no air flow going between the seals. If we know of extremely bad weather we may bring the slide in.
How do you keep out bugs, mice or toads?
We use a "NO SOLICITATION" sign and we have never had a problem.
For real - since we store ours in a garage it has never been an issue. But we have heard to use dryer sheets or real pepperment oil on cotton balls scattered throughout to keep the pesking critters away. We have never had any entry through the slide while we are camping.
The only thing we do is make sure the slide stays in the middle of the opening. There are rollers on each side of the slide and you should make sure the slide remains centered between those two rollers. We noticed a little rubbing on our 2350 and called Kermit and he told us how to adjust the slide mechanism so as to recenter the slide. Apparently one of the nuts and bolts on the slide mechanism loosened and caused our slide to shift a little. Now when Sue is doing the hard job of pressing that button I go on the outside and let her know that the slide is in a good position. We do this periodically just to check.