As I understand it you will need to find a unit and then pay to store
it as long as your are on LI. You will not be there that much longer.
That leads me to think you will be better off picking a unit you will
be happy with for years even if you miss this summer camping season.
Once you move you will have more room and more ways to deal with
things. I assume you are planning on driving accross country as part
of getting into retirement mode so I'm not going into the "buy it
there" rant. ;-) I will mention you can plan a factory stop if you
need something fixed as part of your trip.
There are not many lines left so two or 3 dealers should be able to
show you whatever you are looking for. There is no reason to be loyal
to anyone. You are not going to be around that long. OTOH you might
want to know who can give you factory service at your new home.
Go a bit bigger. A 22 ft C that has everything is possible but
everything is tight. It still takes more than 1 parking space. Open
up to a few more feet and you get a lot of potential elbow room you
will appreciate over time. Often not much time or cost. ;-)
Your milage estimates seem reasonable. Another issue is tow capacity
if you will be towing one of your cars.
Making the bed every time you want to use it becomes a pain fairly
quickly. BTDT. To get a separate bed you will end up with a rear
bedroom mid kitchen setup. There might be a front kitchen but I have
not seen one. I have heard of folks sleeping in the cab over but that
does not appeal to any older adult I know. OTOH the cab over makes
good storage for light weight bulky items like clothes.
Slides add room at the cost of possible problems and losing some
strength in the frame. OTOH I do not think that is a big issue on a
newish unit from a known brand. The folks that are left have to have
a clue. What I do worry about are the way one can use the unit with
the slide in. Some setups are almost impossible to make a meal in
without opening the slide. The sink or stove gets to be hard to
reach. We find that a problem for quick lunch stops or the occasional
nap in the Walmart/rest area type situation where one does not want to
be too obvious or do a lot of fiddling.
One of the cheats is the "shirt closet". Many are too short between
the bar and bottom to hange a shirt or short jacket. Know your
dimensions, take a tape measure, and plan accordingly. One of the
issues is closet space. Another is kitchen storage.
Outside storage can be an issue of you want big lounge chairs or a lot
of stuff. The 22 ft had little, the 28 has a huge under bed "trunk"
with access from 3 sides. Bag chairs in the 22 ft, lounge chairs in
the 28. ;-)
Floors can get interesting. Sit on the toilet and lay on the bed to
check acccess/elbow room. Close any slides and try to get from the
cab to the bathroom and bed. Pantomime making lunch. Those moves
will answer a lot.
Here is a link to Forrest River C layouts:
http://www.forestriverinc.com/ClassCMotorhomes/
Why not start with some you like and ask about them?
You might also want to look at some A layouts.
Here is Fourwinds:
http://fourwinds-classc.com/floorplans.php
We now have a 28z.