I definitely think there are situations for a storage unit can be invaluable. After breaking up with my girlfriend a year ago, and while still in school, I moved out of the two bedroom apartment me and her shared and moved back in with the rents to save money until I got back on my feet. Since I couldn't very well move all of my stuff into my parents house, I got a storage unit where I kept everything (including my motorcycle) over the winter. Now I'm moved out, and as soon as I did I got rid of the storage unit. It was $66 a month, I cleaned the unit when I was gone so I got my deposit back. I think paying a total of around $300-400 was worth it to keep all of my possessions for the short time I had nowhere to put them. Much much easier than trying to sell all my stuff, including my motorcycle, at the beginning of winter. And then I guess trying to buy my stuff back, as Kazi suggested. Plus, from the mustachian point of view, motorcycles have a higher KBB value in the spring than the fall/winter, so I would have sold it when it was at its lowest value. I entertained a few offers for the motorcycle, but they were honestly all well below KBB.
Eventually I sold the motorcycle this last summer. For above KBB :D