This topic comes up quite a bit and I always ask the question but never get a straight answer - Why? Why do you want to leave them down? A stored Rv doesn't care one way or another if it's level. There are a few cases where the storage area may prompt you to want to do it, like a sagging section with depleted airbags where your steps may hit etc, but in general - Why? :h
And as always when this topic comes up, it seems pretty split 50/50 as to who does what. Other than what your manufacturer recommends, I think at the end of the day it's whatever floats your boat.
I can, I have, had one freeze to the ground in winter, so I don't anymore. Couldn't really come up with any good reason why wanted to in the first place. I don't anymore and nothing gained or lost by this decision - other than no longer risking one getting stuck
I will offer this - if you store them down, and you have an issue, you are stuck. If you store them up and you have an issue, you still have options.