TT at semi-permanent campsite

My family is considering getting a travel trailer and we have a few questions. This would be our first RV of any kind.  We currently have a boat and travel pretty much every weekend to a local lake but just spend the day there and would like to be able to stay over night as well.  If we do this we will be renting a yearly campsite at the lake and it would probably not leave very often, but we would plan on traveling with it maybe 2-3x per year for weekends at different campsites, but nothing more than probably 3-4 hours away max.  My questions are around what kind of considerations do I need to keep in mind for a trailer that essentially sits in place all year.

1) What things should I be making sure I check before I leave if sit for a week or more? What items get turned off, what gets left on etc

2) We are looking at units with at least one slide out, do I need to slide these in when not in use? Do I need to get additional support for them if I choose to leave them out?

3) What about the tires? Do I need to do anything special to make sure they don't wear out prematurely from sitting in one place for an extended period of time? I would like to be ready to travel with the trailer at any given time without worrying about maintenance items every time or worrying that the trailer wasn't reliable from sitting for so long.

4) Any specific options I should be looking for with this kind of use?

5) Anything I may not be aware of that I should consider?

I used to have a semi permanent site in New York State;

Item 1;
Water heater off
Propane off
water off
One window cracked open a little, if water will not enter and/or a roof vent open if it has a vent cover
Refrigerator can be left on if you are returning and you want to leave food.  It will  run your electric bill up though. So if leaving for over a week or unsure of when you will return you probably should empty it.

Item 2; I left mine out same schedule as refrigerator. I did not use any braces

Item 3; Tires should be covered to protect from sun damage (UV) and off the ground for protection this is a Michelin recommendation for tires.

Depending on the unit and if you wish to move it from time to time, you will likely need to replace the tires before trying to move it. 6-7 years is considered to be the life time of most RV tires despite the tread wear or lack of it. They tend to rot from the inside out. They can do a lot of damage if they blow out.

My trailer is left on our lot all the time, I always treat it to the same procedure used by others for winterizing despite the fact it will never freeze. Drain the water, tanks, remove filters, place de-humidifiers etc... Note: In very hot and  humid South Florida!!. I always pull the slides in as it give the potential hurricanes less to grab at, no bracing needed at any time, this is not a "park model" trailer with tip-outs. For the last couple of years I have left the power on just to maintain the batteries, other years I had someone cycle the electricity monthly.

Will the trailer have electrical and water hook-ups at the site? Sewer too?  If so, you have some flexibility in what to leave on or turn off.  Generally, though, anything you turn off is safer in that you need not worry about what happens if there is an external power failure or internal  failure in the electrical, water or gas systems.  It's convenient to leave the fridge on, but what if there is a power outage while you are away? The fridge switches to LP gas (if you left the gas tanks turned on), but if that fails to light-off for some reason, you could return to  fridge of spoiled whatever.  But if you turn off all electric and gas, it takes several hours or more for the fridge to cool off again (RV absorption fridges are slow to cool).  Turning off water to the RV is usually wise - no risk of leaks or broken hoses while you are away.

Slides can be left out if you want, but bringing them in reduces the chance of accidental damage.  They do not need any additional support and, in fact, it is usually NOT recommended.

Tires age and age more quickly when seldom used (rolled).  The flexing that occurs as a tire rolls is important to its health, so the more often you move the trailer, the better it is. Unused trailer tires may fail after only 3-4 years.  Some people place sunshield covers over them, but that helps only if they are exposed to direct sun for lengthy periods every day. Parking the tires on well-drained soil or gravel is also of some benefit. Also, keep the tires fully inflated at all times. Most trailer tires need their full rated pressure, i.e. the max load psi shown on the sidewall. 

I would leave slides in and certainly leave any awnings in.  If a sudden storm comes up, it is easy for a slide to catch the wind and have the awning tear. (I have experience in this, and I was inside the RV at the time of the storm!  Did not put slides in quickly enough.)  Best to batten everything down, including chairs and anything else that might blow away.

Good recommendations on the slides...don?t want to be worrying about them while I?m away.