I’ve recently had to deal with my storage rental unit. As a collector and all-around pack rat, I’ve maintained a storage space for over 15 years now. I’ve got some things I am happy to have saved, but sometimes a ready storage unit becomes a good reason not to sort through things, one can just throw things into storage and not have to deal with it. A few months ago this liberty came to an end when the unit reached capacity ~ it was absolutely packed! I discovered this when a large load of items suddenly needed storing, and I had no more room!
My immediate solution was to get another storage space! The new load safely stored, I rolled up my sleeves and started the task of digging through the old space. I did not want to maintain two separate units, so the plan was to dig out the old unit, throw away or repack what I found and move everything into the new unit. The repacking involved some handy plastic tote boxes I found at Costco. 
Unlike the collapsing cardboard boxes that held half of my possesions, these “nestable totes with attached lids” have fold-closing tops, are strong and made for stacking! The clear plastic makes it a breeze to visually find whatever you’re looking for!
Much of what I found in the old unit were items I had stored away nearly ten years ago. There were also some boxes that had been moved from previous storage rentals, so they were even older.
In my reorganization I came across the consequences of long-term storage. Some are rather obvious, such as the undependability of cardboard. Yes, your boxes will collapse if you stack them unreasonably high, or if you stack them crooked. I found some books that were warped into strange shapes because heavy boxes above had been crushing them. Don’t think about storing liquids. If the containers are not upright, time will allow liquids to find their way out of sealed containers. A Fred Flintstone shampoo bottle leaked his assets all over the contents of one box even though he was still sealed in stiff cellophane. Also, keep your valuables dry. I did not find a moisture problem in storage, but things I once kept in a leaky garage were literally eaten away by mold and moisture.
I was surprised to find out about one excellent tool for long-term storage, that being newspaper! Everything that I had wrapped in newspaper came out looking as fresh and clean as the day when I boxed it a decade ago. The newspaper itself had become dried and yellowed, but the valuables wrapped within remained in pristine condition. So my scientific conclusion is: Newspaper absorbs time!
It took a month, but I did clear out that old space. Along the way I found many forgotten treasures and they are now safer than before, stacked in the totes. When I recently moved to a new apartment, it was incredibly easy to visit storage and find some household goods I needed. And I have a new appreciation for the storage space, because although my apartment is of a good size, I am thankful I won’t have to live with the storage goods!
Newspapers do absorb time. They pretty much absorbed 16 years of my life.