Yeah I am growing out of Wall-Bags bags. What I would do for 15g grow bags for like 1$ each.
Don't get me wrong, you get a hell of a lot of value out of a wallmart bags, but If you want to grow trees, 4.5g just isn't enough.
The Gardener's Edge 15g Root Pouch bags are about $3.70 each. Not bad for a 4-5 year lifespan bag.