I'm resurrecting this thread just to comment on it. It was one of the threads I was reading when my living situation changed a bit. I quickly didn't have space for the pins I owned. I didn't want to sell them, because some of them are classics, and those are very difficult to find in good shape now. I already had some games at friends houses, and nobody could take on as many as I needed to get out.
The most consistent advice (not just from this thread) was that it was a waste of money. Add to that the advice that you probably won't be doing much swapping out that seemed consistent as well.
With that in mind, I rented a storage unit. I was very fussy about the place. I intentionally went to tours on blisteringly hot days to get a sense of the climate control situation. The one I picked has excellent temperature and humidity control. I keep a temp and humidity sensor there, so if things go too wonky, I'll know it happened. I also put in a huge rack for the heads legs and bolts. I built platforms to keep the games off the concrete (2nd floor to get less temp variation).
What I'm finding is that I swap the "downstairs" games a lot. I can wheel them right out of the basement to my car in the garage. The drive is about 15 minutes each way, and then poof, that fresh game feeling.
Before doing this I was looking for a place I could rent to setup a game room off site. Unfortunately the costs of that were much too high, and I felt if they were setup elsewhere, I'd never go play them. If I'm going to play, I want the game here. But really, the cost made that option impossible.
Costs. I consider them very reasonable. My storage unit is all indoors, and you drive your car inside. The drive through is massively convenient. Because I put the game into the car in my garage, and I unload it inside, I don't worry about the weather. That does add costs, but a cheaper place wouldn't meet my need. And it's less than my cable bill. So overall, what they provide is totally worth the costs. And if they start raising costs quickly, I am totally prepared to rent a big truck and move all the games to a different place.
Doing this depends on a few things:
Do you keep your games in good shape? I'd never move a non-working game there. A game that gets moved there needs to be working 100%. Otherwise you will be annoyed as you not only just moved and setup a game, but now you need to fix it. Sometimes that will happen, like an EM that sat too long without getting played, but that is a quick thing to get running.
Do you have a vehicle that you can just toss a pin in? You don't want to have to arrange or rent something. You want to be able to just pull a game and swap it when you have time and when you feel like it.
Are you able to move games yourself? This goes with the one just above. If you have to arrange help, or anything, you probably won't swap games enough to make this work out.
Will you swap games? I do. And I love that when I move a game into storage, I know that 6 months later, it feels new to me. If I'm bored with a game, I sell it. But when I move it to storage, I know it has plenty of fun left to give me. But if YOU are not going to do swaps, don't get a storage unit. I think this is the most critical thing. If they all sit there dead, you really are just wasting money.
Is there a "real" climate controlled storage near you? As others said above, temperature fluctuations kill pins. Your backglasses will start to go south, you will get planking, and rusting, and generally bad things no pin should have. If a place looks good, but then you find it isn't, get your games out immediately.
Is the place actually secure? Pins are valuable. Insurance is great. I extended my homeowners for this. It had a small amount, and I added to cover things. But really, how can I replace my 4 Square? I can't. So make sure the security at the place you choose is real. If they have one driveway camera and that is it, don't bother. If the door of your unit isn't clearly visible on a camera they can show you (and check their retention policy for footage), again, don't. I realize these are high standards, but again, where am I going to find another 4 Square like mine? I can't.
Conclusion: For me, adding a storage unit fixed my space issue. I swap games often, and I seem to be giving more attention to games while they are here (I think just because I have less games in the house). I really like standing in the storage unit deciding which game to bring home. It actually allows me to also know that I don't want a game. Last night as I chose, one game that I hadn't played in 6 months was sitting there, and I had no urge to play it... so it will get sold soon. For me, this is working very well.