The purpose of the levelers is to level the rig, not prevent tire flat spots or reduce suspension stress. In fact, if the field is already level, neither of those "benefits" would occur. If the field is not level, the "benefits" would occur unevenly across the 4 corners.
Level the rig for the non-residential fridge or for your comfort.
I keep my jacks down because I am often extending and retracting the jacks not for suspension relief or flat spots.
The only way to reduce tire flat spots would be to have all wheels off the ground. And that is a definite no with all leveling systems.
Trying doing what is best and drive the coach once a month to exercise the systems and warm up the tires.
Agree on taking it out and about when the weather is right. I live in MA and near NH line so snow and longer storage is the usual Dec through Feb routine. This year was different with COVID. We left mid Jan before the bigger storms and are returning to, hopefully, all melted snow warmer temps and drier ground.
"My question is???*Should I do a self level/or a manual on the rig to reduce stress on the suspension while in storage ??"
Manual leveling is an excellent idea especially on grass, 10 points of contact
But before lifting you can spread the weight even better by using something like 2X12X2' wood under all 10 points of contact.