A couple of years ago my brother and I split all of our old legos. He spent the better part of a year assembling all the sets we had, looking up instructions online if needed and buying bricks to replace ones lost over the years. We then calmly and evenly divided what we had. My Dad expected more heated arguments, but we were quite reasonable about it. I've been building my half with The Boy (who will be 6 in March) for a while now. My brother is just starting with his oldest, who will be 5 this summer. He is also buying new sets and smuggling them into the house under the wife-radar for when his boys are the right age. He's an unabashed LEGOholic.
It is interesting to see the evolution in LEGOs. The original yellow castle, everything was basic bricks, even the horses for the knights. The most recent King's Castle (which my folks got The Boy for Christmas) is chock-full of specialized pieces. Some are cool and neat, like the lion head capstone brick over the gate. Others are not necessary. "Back in my day we just stacked 4 1x1 posts on top of each other to get this piece"
Kids these days.
Get off my green base-plate!
(They probably have custom lawn bricks now anyway...)