While it is easy to get caught up in the hype for a new smartphone, you don't need to upgrade with each new model. Especially as these devices can get expensive. The latest iPhone announcement is a great example of updates many won't find necessary. It's probably appropriate to wait about 3-4 years before upgrading your phone. It's also better for the environment to not throw out all those old electronic parts so frequently, though there's at least a decent market for used phones these days.