Without seeing what's eating your battery in Settings, I can take a SWAG:
It's not the texting that's getting your battery... it's the SCREEN TIME. Sounds like your display is running a lot; and that gorgeous Super AmoLED Plus screen is chewing through battery.
I can recommend TWO things:
(a) 2100 maH extended battery. It provides 17% more juice and increases the phone's thickness by a mere 0.5mm.
(b) Juice Defender in the Market (or Play, or whatever it's called now). The free version on default settings will help you significantly... the Plus version will help you a whole lot more. Try the free version and see how that works for you.
Between those two things, I can pretty much go all day with occasional texting, phone calls, web surfing, videos and nearly constant bluetooth music streaming.
Hope this helps