Besides the common basic sets like the box-of-pieces sets, every Lego set will be discontinued. I would also argue that most AFOLs will be able to reasonably ju

Besides the common basic sets like the box-of-pieces sets, every Lego set will be discontinued. I would also argue that most AFOLs will be able to reasonably judge which sets will be good investments and which ones will not be. It also used to be reasonably easy to tell if a set was going to be very popular based on how it did in the 'VIP presale' (where you can only buy the set if you're signed up for Lego's loyalty program) But you're right about the storage. The sets that appreciate well tend to be the larger ones which necessarily means larger boxes and more storage requirements. And we're still only talking at most several hundred USD per box for the majority of sets, so 'density' of investment is pretty low.