I honestly don't see why having it in a raised condition for a long period should be harmful, but the top IS being held up by the lifting cables that way, and I suppose they could stretch a bit. Also, it might settle down on the safety bar if up for a long period and this MIGHT distort that bar, which would be something you don't want.
Given those two possibilities, I suspect it would be appropriate to place four 2x4's between the outriggers and the top that are cut to a length that will just fit and would support the top if lowered on to them. This then, would support the top the same way the outriggers do when it's down.
However, when I've been working on my trailer at home, I've had it up for a month or so without having any damage.
- Jack
