My guess is that no one wants to be accused of packing a storage unit like this:
One way of combating this problem is to think about what you're storing and for how long. List the things needing to be packed separately, or require special attention depending on how long and type of storage? A few examples, wooden furniture that may need some wood preserving oils, electronics should include moisture absorbing bags or alike and wash machines may need to be winterized if stored in cold storage areas.
During the packing process use plenty of bubble wrap, newspapers, blankets etc. to ensure things don’t break even during the ride to / from the storage facility. Things shift around and sometimes rough handling occurs during the loading and unloading process so the better you protect things the better chance things will not get broken or damaged. Lot’s of tape on those boxes is a must! Labeling the boxes will help later when you’re looking for something.
Once at the storage facility, take time to plan a packaging strategy, this will make the best use of available space. Heavier boxes and bulky items are best on the bottom and things such as cardboard, cloth, bedding etc. should never touch the concrete. Instead put these items on top plastic bins, pallets, 2 x 4’s or alike. Prioritize the items that may be needed more frequently and should be stored last or toward the front of the unit. Items needed infrequently should be put towards the back.
Include in your plan and the reason for considering a unit one size larger, an isle way usually down the center for easier access to the items towards the back. Lastly don’t for get the ensure that the door latch is securely in the locked position and the door is pad locked!
Regards and Happy Storing!