At the seasonal lot...everyone leaves them out. I only close mine in the winter storage months...and many don't even do that. Ours don't leak...no matter what Mother Nature has dropped. So far...so good.
Good suggestion...to move them in and out once in awhile...and maintenance is important. Seal lube would be a great idea...to maintain those seals.
Another thing to note: Those slide roofs will be exposed to more gunk, debris, bird droppings, tree sap, leaves, squirrels, rain, hail, etc. Keep them clean, and check them often...as they may need extra attention.
We leave them out all summer...but I'll be sure to roll them a time or two and dress the seals.
Pete (Jolly Mon)
2014 Jayco Whitehawk 24 RBS
2004 Nissan Titan LE, 4x4