There are a few types of toys that my wife and I are still ok with getting and Lego is one of them. She's started using the phrase "more really is more" to describe the category. Basically, it's systems where you build something and the more you have, the more things you can do: Lego, Brio, Magna-Tiles, Hot Wheels track, etc. Even things like Pokemon cards (if your kid actually plays the game) can fall into this. You do have to be careful not to end up with too many of these systems, especially really similar ones.

We're also still ok with getting books. We have a few too many for our shelf space, but at their current ages, our kids are aging out of books about as quickly as they receive new ones. I just need to do a better job of giving away the old ones more regularly.