Sometimes onsite storage isn't enough space for your items. I can't believe that I just said that! Someone smack me!!
On site storage is the unit that is provided by your condo. If you are in a vintage building, you may have a walk in unit that looks like a horse stall(like this lucky chick) or you may have what I term is the cage type storage.
This storage is either in a basement or located on your floor. Its semi cold storage. You don't have to leave your building to get your items.
In this type of storage, you should have things that you use once in a while. Yes, I am talking about your summer gear(everyone has stuff for ravinia or outdoor concerts). Offseason clothes should be in this storage as well. We all know that Chicago can change seasons in one day. Paint for touch ups should be in your onsite storage as well. And let not forget your tools. Wrapping paper is another good item to store in this unit. And last but not least, your paper archive box. Yes, I am talking about your taxes and mortgage papers.
Off site storage is that in which you rent. If could be a few blocks away or miles depending on the place you choose. This should encompass your holiday decorations and memory boxes. You should also keep any home decor or furniture that you aren't presently using but want to keep. Also items that have been inherited from your family that aren't displayed in your home can reside here.
Evaluate what you need nearby and what you don't mind driving to retrive. Use uniform bins that stack. This gives you more space in your unit. Try to containerize as much as possible!!