Unfortunately Buff this is an issue with all iPhones. The batteries are not easily replaceable and they wear out. Rechargeable batteries are a consumable item yet you can't just pop in a new one.
If you are in love with your iPhone have the Apple store put in a new battery. If you just love iPhones in general, understand that this is Apple's way of making you upgrade and go buy a 6.
If you aren't tied to Apple go buy a Samsung S5 or S6 in April that you can replace the battery whenever you want or even have two batteries so that you never have to worry about it.