Tsk Tsk for not reading the front page.
Clicky.
5) Sleep mode. One of the drawbacks to a disc-based system is load time. To help overcome some of the boot-up and loading time for the PSP, it allows you to put the system on sleep mode with a flick of a button, when you have a short break. Turning it back on will jump you immediately back to the point where you left off in your game, in less than a second. Furthermore, sleep mode has been found to have almost no effect on the battery-life, even after being in sleep for 24 hours. This means you can play in short bursts, experiencing the benefits of disc-based data, but minimizing the load times, if you need to keep it off for a little while.
And this was a follow-up article , pointing out the bad side of the PSP.