Well,
Whenever this topic comes up, it's always a presidential debate. Not really sure why but, it happens. I guess it's just like a lot of other topics that are generalities. It's actually quite simple, you either leave your jacks up, or, you put them down. How you justify either way, is of course, up to the individual. Many claim there's value in taking the weight off the tires when in storage by using the jacks.
I'm not a tire builder so, I don't have a clue whether taking any weight off them is of value or not. If it works for them, and, they think it's of value, well, have at it. If you don't put them down because you're the kind that thinks the worse will happen and, you won't be able to get them back up, well, maybe you should NEVER put them down again.
Nobody knows if and when, anything will go wrong with the jack system. If it's going to happen, it will, no matter where and when. There's only a few zillion hydraulic rams being used all over the planet on every kind and piece of machinery there is and, in the worst operating conditions possible and, a massive amount of them are left in the extended position, from day to day, week to week, month after month and, for the most part, they're still kickin'.
I'm certainly not chastising any one here for putting them down during storage or, keeping them up. It's everyone's choice. While there has been some reports of issues with them, here and there, they're not as delicate as some think. The main difference between most of our jack systems on our motor homes and, the rest of industry is, ours are tied to computers. Most of THEIRS are tied to simple hydraulic valves attached to levers, to make them work.
Much of the time when issues are reported on here about jack systems, it's because of the computer/solenoid operations part of it. Sometimes it's weak springs. On rare occasions, it's a bad seal that keeps them from being retracted.
But, unless you live at the oceans edge, where salt air and water are lapping up against the exposed portion of the rams, they're not going to rust out from under your coach anytime soon. And, with just a tiny bit of preventative maintenance, like about 3-4 minutes total of a little spay of something like WD-40 or, whatever you choose and, wipe them down, you're good to go for quite awhile. And even that is only needed about maybe once every couple of months, depending on the environment.
So, again, it's up to the individual to choose, there is no right or wrong. You do it (extend them during storage) for your reasons. Or, leave them up, again, for your reasons.
Scott