this is done on purpose so that you'd have to replace your phone every 2 years
I have a 4S and the home button is beginning to exhibit cracking sounds when I press it.
apple's business practice is just as nasty as other corporations.
That's unfortunate. I was able to upgrade a couple months ahead of time. Got the iPhone 4 (verizon) when it first came out in feb 2011 but Verizon let me upgrade in oct 2012. I didn't see a reason as my iPhone 4 still works and I could probably use it until the 5S came out. Only bad thing is that my home button wont work at all sometimes.
Apple will eventually ditch the home button. That would be Ive's dream. The front would be completely flat thanks to haptic, virtual button. They're trying to take it feel like a physical home button but of course, its not actually a physical home button.