If you are rough on your iPhone, you should consider getting this Otterbox iPhone case. They are guaranteed for life, and virtually indestructible! You can get this Otterbox Defenders Series Hybrid Case & Holster for iPhone 4 and 4s for $17.75 + FREE Amazon Prime or Super Save Shipping! (Reg $49.99).
As you know Amazon prices are always changing, make sure to snag these before their prices go back up!