our kids lego goes back th the late 70s. some may even be older because already then we were getting lego second hand. my dad kept our lego and passed it on to my kids, and when they grow up i will do the same and keep the lego for my grandkids.
we'll pass this from generation to generation until the plastic degrades to unplayability.
My son is still playing with basic Lego bricks that were my older cousin's bricks in the 80's. The amount of plastic waste we've caused and gone through in the last 40 years is many many many orders of magnitude higher than those few sets :|