How long do iPhones normally last? - 1

My upgrade is coming up in a few months (I'm with AT&T), and my mom said she'd give me her iPhone (that she's had for about 1 year now- I think it's the 4s) instead of buying me a new phone.
I'm not picky about phones (I've had the LG Vu and the LG Vu Plus, and my moms old Blackberry Curve), but if she gives me her iPhone, I don't want it to start malfunctioning in a year or two.
So how long do iPhones normally last- their durability and battery- if you take care of it?

They last until you drop them one time. Don't get an i-phone you'll have a cracked screen in a week. Go Android and get yourself a Gorilla Glass screen that will NEVER crack no matter how many times u drop it

Technically I don't think AT&T would view this as an "upgrade" unless you re-signed a two year contract… Maybe I'm wrong.

You'll be able to get a new phone at upgrade time for a discounted price.

It all depends how hard you are on phones. If you take care of them, they should have no problem lasting for a couple of years easy.

Typically several years, if you take good care of it. Some people are more rough with their iPhones which shorten their lifetimes.