Mine is in an OtterBox Defender, and even with that maximum protection I still remove it occasionally to clean it and the case.
I used an OtterBox Defender for my iPhone 3GS also and I got top dollar for it when I sold it because it was in such pristine condition. This, despite the fact that I carried it every day at work, in an environment that is not friendly to any kind of cell phone.
There are some who don't like the looks of the OtterBox Defender cases, but they give almost bank vault protection to your phone while allowing full use of all the phones features.
I have no ties whatsoever with OtterBox, I'm only a satisfied customer.
Your Milage May Vary.