There's no requirement that you actually implement a patent to keep it. The patent troll industry runs to a large extent on patents that aren't being practiced.

There's no requirement that you actually implement a patent to keep it. The patent troll industry runs to a large extent on patents that aren't being practiced. You may be thinking of trademarks, which can be granted on the basis of an intent to use the mark in the market with a time limit thereafter to keep them.