Merely turning your phone on may be enough to prevent it from sleeping. What I'm about to tell you is 100% repeatable. I've done it about ten times now; it has happened every time. I'm running the stock Android 2.1 ROM from Sprint. <Background> When Android boots, it preloads a huge number of apps into RAM. Essentially, it's starting JVM processes and loading the classes of applications without actually executing any of their code. Android does this to reduce the lag you would feel when activating one of these apps. These preloaded apps are said to be EMPTY. There's no real penalty for preloading these apps since they're loaded in the background in otherwise idle CPU cycles and their processes will be terminated as needed to free up RAM for applications you begin using. </Background> Although it should be impossible, one of those preloaded apps is preventing the Hero from sleeping. By process of elimination, I have found which one it is: Footprints. Here's my test case, which I can repeat every time: Boot the phone from cold. Go have a beer. I'm only partially kidding: it doesn't have to be beer, but do something (not on the phone) for a few minutes. The phone needs to be allowed to finish preloading all of its applications, which it will continue to do in the background even after the launcher becomes usable. Return to your phone to find its screen off. You only think it's sleeping now. It's not. The CPU is quietly draining your battery. Unlock the screen and press "Menu, Settings, About phone, Battery." Notice that the "Up time" and "Awake time" are the same. D'oh! Go back Home and fire up a task manager. I use Estrongs. Find and kill the Footprints app, which should be listed as "EMPTY." Now press the power button or simply wait for the screen to turn off. Wait for 10 seconds. Press the power button again to turn the screen back on. Unlock the screen, go Home, and again press "Menu, Settings, About phone, Battery." "Up time" will be approximately 10 seconds longer than "Awake time." Conclusion: Killing the EMPTY Footprints app allowed the device to sleep. You don't have to exactly follow the above sequence of steps, either. I've done other things after booting but before killing Footprints, including making phone calls both with the built-in phone and with Sipdroid, killing other applications besides Footprints, turning the screen off and on, and rechecking the Battery info. Basically, until you've started enough other apps that the Footprints app gets killed to reclaim memory, your device will not sleep.