Maybe you have an iPhone 4, and you're very happy with it. Just a little wear and tear, but no need to upgrade yet.
Maybe you're waiting for the iPhone 6 to come out, but when???
You'll probably find this video - Make your old iPhone run like new - by Donald Bell very useful. It has some tips and tricks to clean up your iPhone and make your life a little easier. You know that game that was FREE and looked really fun in the App Store.... had to connect to a WiFi network to download it.... yeaaaaaah, you never play that, do you? By deleting that huge, space-sucking game off your phone, you can make it run a little faster.