If best buy/future shop etc offers the extended service plan with phones down there for $15 a month get it. Especially if you use phones like the S-series that are screwed together and you don't need a case opening tool.
The ESP covers everything except broken screens and water damage (two most common things) but if it breaks in any other fashion you can get any replacement phone you want.
First off buy OEM knockoff batteries from China (likely no NFC) but still I got 3 for 15 bucks and a charger for em. Don't use your samsung battery, it has a litmus strip on it, employees check it, so if it gets wet youre fucked. Most employees don't know dick about the fact that they put one in the headphone jack as well.
So now to explain why this plan kicks ass. First phone $650 galaxy nexus, rooted it, put on an app that increased speaker volume, blew the speakers and dislodged the vibrating motor. Brand new galaxy nexus again (I didn't want s3). Then I dropped it on the ground busted the hell outta the screen. So I bought a cheap digitizer from China ($120) opened it up popped out old screen put in new one. Disconnected the charger from the mobo, brought it in got the S4.
Now soon to pop this bitch open and disconnect something for the S5, I can even technically dip the bottom half in water and bring it in, these workers don't know shit. One employee told me about a dude who changes his phone every 2 months and started asking me tips on how to break his iphone hahaha