The iPhone has been prone to power button issues ever since the iPhone 4 made its appearance. As it turns out, the iPhone 4S isn't immune from stuck power buttons either. Over time, the cable wears down and causes the actual power button to become harder and harder to press. In some cases, it becomes completely recessed resulting in presses not even registering.
If this issue sounds like something you're iPhone 4S is experiencing, a DIY repair can get it back to normal with some patience and the right tools. It'll also cost a heck of a lot less than a brand new iPhone.
If you're up for it, follow along. And if you're not, follow along anyways and we'll refer you to the professionals that can do the repair for you.