Here is my favorite parenting trick. When your kids are sleeping, go through their toys. Pull out anything they're not that interested in at the moment (ideally, this will be about half of their toys), and put them in a bin. Put that bin away. In 3-6 months, swap out their current toys for the toys from the bin. Your kids will feel like they have brand new toys...simply because they haven't seen them in a while.
There has been a study that shows that kids with an average of 238 toys, only play with about 12 of them (put another way, kids play with just 5% of the toys they own). The less toys they have, the better they'll play. Not only that, but they'll likely treat their toys better AND they'll be much easier to pick up when there's less of them.
When kids see toys as something they play with...but can be easily replaced or upgraded, they don't place a very high value on them. If they treasure their toys, because they don't have a million other ones to play with and destroy; how do you think they'll treat other things and/or people in their lives?
Teaching our kids that every thing has value and purpose, also teaches them that everyone has value and purpose. It teaches them to be good stewards of our earth and our resources. It teaches them to be gentle and kind to toys and people. And that's worth a lot more than the toys we give them.