It used to be that a 3.5 inch screen was enough on an iPhone now look at the Samsung Galaxy note 3 which has a giant screen. People want bigger screens, I agree that some screens are way to big but even a 4 inch screen is to small for most people. Anyway I'll stick with Android.
I have my 4S, it is going really well, I actually went and tried a bunch of Android phones- which are now in a drawer as backup phones because I hated using Android haha.
But yeah, I hate all this wasteful society, upgrading to the latest only because they have to have the latest gear.
I'm sure a bigger screen is nice, but these things aren't exactly free. If there's nothing wrong with your current phone, the existence of a better screen doesn't suddenly make your phone bad. "The grass is greener on the other side of the fence" is a matter of perception. I will replace my phone when it needs replacing. No sooner.
When we first got cell phones, weren't we all happy as they began to get smaller and smaller over the years? Now it seems that we are happy when these phones get bigger and bigger. Pretty soon we will be carrying around computer sized devices that we have to use a bag for.
I don't have an iPhone, but I wouldn't upgrade for a larger screen. I don't have or want a smartphone at all, no matter what size the screen is. I'm obviously in the minority, but I hate the idea of carrying a phone on my person and being on call everywhere I go, 24 hours a day. People have no sense of privacy anymore. I'm going to hold out as long as I can.
It is another pointless feature, as the larger the screen, the further you need to be away from it for optimum viewing. Phones such as the Iphone 5S and the Galaxy S4 have big enough screens, and the only benefit of the larger screen would be if it was higher quality. The price is also going to increase if it has a bigger screen!