Another thought - I really should get all my thoughts together before posting lol - is: Don't feel like you have to do it all at once. Do one box at a time. Or just half an hour a day until it's done. Whatever works for you. Where to start - at the first box you see.

The rotation box that Tanstar mentioned is a great idea too. I do that for my DS. He rediscovers toys that he was previously bored with and they last a lot longer.