Good points made by one and all, and appreciate the feedback. Where I park is slightly off-level, probably 3 to 5 degrees front to rear, and about the same from right (passenger) to left. Definitely enough slope I need to level while moving slide.
While I have a canvas cover for rig, it's too much for wife and I to safely maneuver on and off. I don't think first owners ever used it either. No covered port available at this time. I keep it on 120v shore power every other week to keep batteries charged.
Think I'll probably wind up "splitting the difference" - keep things buttoned up most of the time, and level with slide out when there's a reasonable chance of getting any pre-season chores done. While I have it all closed up, will probably take it for a few spins around the block periodically to keep the tires round.
Will definitely take the opportunity to lube the jacks as Bob recommended. Would silicone be recommended for that application, or something else?