We moved a few months ago, and even now about 90% of their toys are still packed up in boxes. No exaggeration. We didn't make a thing of it, we just quietly decided not to unpack anything by default - neither kids' stuff nor parents' stuff - and instead only unpack specific things when someone specifically wants them. Because how often do you get such a good chance to find out which of your possessions you actually care about?
So far what we've seen is:
1. Less sibling conflict.
2. Less complaining about being bored.
3. More creative play.
4. Zero complaining about not enough toys.