Good advise so far.

An alternative is just to wrap the packed backpack in saran wrap. It contains all the straps and buckles but at the other end, you just peel off the Saran and you're good to go without having to deal with a place to store another piece of carrier luggage. Sometimes, if you are relying on public transportation or trail shuttles to get you to your hiking destination, there's no car or motel where you can leave stuff for later pickup.