Well, he never did grow completely out of it. He's pretty good about listening when he is on the leash and sniffing at it and we tell him "off". However we have a longer line attached to the deck so he can be outside by himself in the back. Sometimes when we let him out this way by himself I'll come out to get him and catch him in the act of eating it.
He also likes to eat the sleepers from his eyes. I'll remove them from his eyes once in a while when they get bad, and he always tries to eat them after I do.