I give my boys an unlimited amount of chew sticks almost every day. Apple wood is safe to give every day to a chin as they will mostly just chew off the bark and not necessarily ingest it like food. Chins need to chew so I would not limit him on the wood whatsoever. If this is the first time your chin has had apple wood he's probably just excited at trying something new and will go back to his business of eating his normal amount of hay.