Here, here, Roy!
The great news is that since you don't have a water system, you can camp as long as you want into winter until it just becomes unruly. I lived in northern Wisconsin right at the edge of the snow belt so 143cm of snow is typical. That made for some fun camping.
Without water, your biggest concern with dropping temperatures would be how the vinyl is going to react. Everything stiffens up and I get a little nervous about the clear window vinyl as it approaches water freezing temperatures. There's nothing magical about 0 degree C for vinyl but it really gets stiff and I'm afraid it will break on me the older it gets. Some folks will turn the furnace on high for a while right before closing up the PUP to keep the windows as pliable as possible. I haven't ever gone there.
Anyway, if you keep your tenting mindset but also don't go crazy on loading up all of the accessories you can get your hands on, you'll really like the PUP life.
The add-ons you have listed are great additions. I don't have proper Reflectix for my windows but use the silver-tinted automobile sun shades. Otherwise, I've got the rest and know them to all be helpful in keeping the temperatures inside I want. I'm about to head out right now and facing highs around 34 C. Come on air conditioner and PUGs!