Keeping Jacks Down for Storage to reduce tire flat spots

Never heard of "flat spots" being an issue - have heard that tires need to be exercised occasionally to keep the chemicals within the tire distributed to prolong life. Doubt putting the rig up on jacks does anything to prolong the life of the tire.

I have always heard that RV tires tend to rot from the inside - your tires are well beyond the norm that most RVers would consider safe. If it were me I would have the tires unmounted and inspected by a tire guru. Just my 02.