We collect boxes as well. They stack up until we get a pallet load, then burn the entire pile, with the pallet. If one listens carefully you can hear the pallet scream out in pain. The burned up pallet always seems to leave a nice supply of nails that seem to jump out and attack my tractor and mower tires.
Walmart boxes are by far the best, but they don't compare to any poorly made pallet. I'm sure that online buying is grossly adding to the box supply. Even termites avoid my pallet supply. The pallet supply usually comes from the 'feed store' at no charge. Strangely, the local hardware store wants to CHARGE $5 each. How dumb is that?
