I also went through this thought process...
My research about tires is that leaving them sit with weight on them for six months does absolutely no harm... other than flat spots. Flat spots smooth out after a mile or so of driving, and again... no harm to the tires.
I store my MH in the back yard. The only reason I level it is to bring the slide out, or to run the fridge... both require level. Otherwise, the jacks are retracted. The rig is covered in winter, so I neither run the fridge or bring the slide out... and with no harm to the tires, the jacks remain retracted and the rig sits unlevel with weight on the tires.
I have zippered panels on the cover I open once a month to run the generator, check batteries and look inside for leaks, etc.
I figure keeping the jack rams retracted is a bonus... not exposed to the elements and keeps them clean.
That's my 2¢.