Thanks for all the tips. Since I made the post I have done a lot of research, and have decided against the brush buckets for now. We have found a wood supplier from a pallet factory, and are planning on doing stake buckets instead. I will keep in mind about the blocks for the brushpiles later on.
Actually, except in VERY fertile waters (southern swamps basically) osage orange (hedge apple) will last between 20+ to 30 yrs. In low fertility waters (freshly dug gravel pits) at 15-25 fow they can last 45+ years...