Use Common Sense
These phones are very valuable, and they cost money to maintain. This is no surprise to anyone. I have an Otterbox Commuter case on my phone, with a screen protector from I dont remember what company. I worked in a pastry shop for a year and was constantly around tons of sugary dirt, and had powder on my clothes and hands all the time. The otterbox performed outstandingly, and all that was required of me was to use common sense: Don't expect your phone to remain immaculate forever when you fully know it will not, but make preservative efforts so as to make it last as long as you can.
Most phone contracts last for what? Two years? You can be careful with an expensive device that you need to keep for that long. Just be respectful of it, don't be a wild animal throwing it around, and just act like the adult you are. No matter what you do, if you drive your car, it will eventually get some dirt on it. Same thing with a phone. Just be a good owner, and take care of the phone (car), knowing that it will be taking a bit of a beating while you own it. There is no need for threads this long about how upset we get about scratches. It's part of the phone contract. You get a new one every once and a while. Just relax, and treat it with respect.