If you haven't traded it in or sold it just yet, there are tons of ways to repurpose your aging phone.
Remember, smartphones are just miniature computers, which means there's a lot you can do with them even if your phone isn't activated or connected to the Internet. Don't let it get dusty in your desk drawer.
You could use it for extra storage.
Unless you opt for a bigger storage option like 64GB or 128GB, your iPhone is bound to fill up quickly. You can always use your old iPhone to store some extra files.
Use it as a music player.
Afraid you'll drop your giant iPhone 6 Plus when you're out for a run? If your music library is already on your old iPhone, you can always use it as an MP3 player for those times you may not want to bring your new phone with you.
And while you're at it, you can use your old iPhone 5s as a step counter.
The iPhone 5s has a co-processor in it that keeps track of your health data. If you don't want to bring your new iPhone 6 on a run with you, the iPhone 5s will serve as a great pedometer and music player.