It’s that time of year again. Although it’s a few months later than previous years, all of the pre-iPhone launch festivities have begun. We’ve seen blurry spy shots, several glimpses of leaked parts and cases, and heard countless rumors.

Now, all that is left is for Apple to announce the media event. But as we get closer to the iPhone 5 unveiling, folks are pondering what do with their soon-to-be-old iPhones. Well, if you plan on selling your iPhone 4 online, you may want to do that in the near future…

It’s essentially the circle of life in the world of Apple gadgets. A new device purchase is usually justified by selling off its older model to recoup the cash. And naturally, people take to sites like eBay and Craigslist to handle the task.

But BGR is reporting that if you are planning to sell your old iPhone, you better act fast. Based on research done by electronics recycler NextWorth, the value of iPhones decrease as much as 15% immediately following an announcement of new models.

Those looking to sell the iPhone 4 specifically online might have an even tougher time, as there have been countless rumors of a low-cost, updated version of the device coming this Fall.

What do you plan on doing with your old iPhone? Selling it as an unlocked device always helps.