I've never been a seasonal camper, but I'll add my 2 cents worth! If I had a seasonal site, I would put the slide in when leaving and lessen any chance of a leak as well as protect the seals from the elements. Likewise, why leave an awning out and exposed to the elements if you aren't there? And, you really have to know the area where your seasonal is located to even contemplate leaving an awning out.
As to the black tank, I would probably use my flush king and keep it emptied while not there...being sure to keep some water in the tank. Yes, it shouldn't be a problem leaving the tank for a week, but I would just rather empty it and know that I have an empty tank when I return the following weekend. But...that is really just a personal quirk!!
