My wife and I play iPhone hand-me-down every year. Of course I get the newest model and she gets the previous year's. BUT...(wink-

-hint) I do one thing. As my iPhone is at the end of it's 10th month, I go to the "genius" bar complaining that the screen locks up. They open a case number and tell me to go home and do a clean restore.
4 weeks later I go back and say "It still locks up sometimes. Usually while web surfing but sometime while sending texts. Just a couple of times a week". They whip out a replacement iPhone but I object. "I don't want a refurbished phone that was someone else's problem." Apple say's "We don't put our refurbished iPhones as warranty replacements. This one is new and unused but without the nice box and accessories."
I go home with a new iPhone with a fresh battery and no scratches. A month later when the new model arrives, I get it and hand down my "used" phone to my wife.