Why does my iPhone die extremely fast?

Alright, so I have had the same iPhone 5 since April of 2013. It's literally in perfect shape, I keep it in an otter box so it has no scratches, cracka or anything else like that. Lately I've been noticing phone battery has been dropping at a rapid rate throughout the day. I'm talking like 20% within an hour and a half. When I sleep at night I'll like press the button to sleep it (phones not turned off) at about 95%, wake up and it's on 71%. I use to be able to sleep and my battery would only drop a percent. Mind you my phone is in perfect condition, I have my brightness at a decent level, refresh app in background turned off, everything. So what could be the problem?

HAve you used the device while it charged? That damages the battery, and a damaged battery can do just that. You must go to your wireless phone dealer for a new battery.

Maybe try a more balanced meal, or possibly a low cholesterol diet. If you don't won't it to DIE you've go to give it a TRY i always say.

The batteries in the phones are designed to last at the very best two years in most cases they only last about 1 yearalso have you installed the software update for iOS 7 if not do it

Try to run the battery down as far as you can (like you can't turn it back on again without recharging), then recharge it: sometimes batteries need to be 'reset' like that.