Well, yes and no.
I'm not a trader. I buy what I really love, and generally only sell if an improved version comes along, and for 95%+ of my collection, that's never happened, so to me, boxes are a waste of space, really. I never need them again, and the only reason I keep them is because I have space in my roof category.
I certainly wouldn't be spending money on a storage unit to keep them on the off chance that in 10 years I might need one of them. That's a wasted expense, you've already spent far more on storage than the box is ever likely to be worse, and most of them time, it's simply not going to be worth it. Plus, as a kid, having ripped open and played with items that are worth many thousands today in MISB, screw it. I was a kid. I played with them, got dirt on them scratched them, and in a lot of cases broke them, but I enjoyed playing with them.
Isn't that the whole reason we collect? To enjoy our purchases? To make lightsaber noises as we play with things like our lightsaber prop replicas? To put our HT Batman in a kickarse pose on our shelf, so when we look up at him that little kid inside says "fooook yeah!"?
Even fairly recently, I bought a Palisades Muppets Backstage set, MISB, and first thing I did when I got it was to open it and pose some Muppets in it, instantly blowing hundreds of dollars, but man, it looks great on my shelf, and I smile every time I see it.
Screw it. You live once. Enjoy what you have, worrying about some financial appreciation that may or may not happen in 10 years is just stupid.