How long do iphones normally last?

Ok so i got an iphone 4s (unlocked) at the beginning of the month i also got applecare+.im 15 years old (and a half) and i want to be able to use this phone until i'm 18 so i can switch to my own plan (i know this is early planning but thats just what i do) so i was wondering how long an iphone should/ will last (if i don't drop it or anything)

Well mine lasted 10 months (I dropped mine in the toilet… ) iPhone are very well built, but an act of carelessness will do it in. Buy an Otterbox, or a heavy duty "life-proof" case. If you take good care of it, it will definitely last you until you're 18.

My old iPhone 3GS (released almost 3 years ago) still works fine. No hardware or software issues.

Assuming you don't drop it from a large height and generally look after it, it will last a good while.