Each time my Archos G8 is not used for some time (say 30 mins. to ... ) it shutdowns or goes into deep sleep... After I press the power button it then boots again taking the normal booting time. Is this a normal behavior? How can I configure the amount of time before the device goes into this mode? Trying to find this in settings but nothing points to this explicit. And I don't have deep sleep activated in the battery settings.
Not that I don't like this; sometimes is best then really completely discharge and then having to wait a long time while it charges back again into life.
If you have upgraded to 4.0.24, or 4.0.25... those are both complete garbage and do not work at all correctly.
If you have upgraded to 4.0.26... although some things have been fixed, there are still MANY PROBLEMS with it that need to be fixed in a future firmware upgrade (including shutting down for no reason, not charging properly, and a bunch of other things).
On the other hand, if you were already having this problem with earlier firmware (only good ones were 3.2.80 and 4.0.7), then there is either a hardware problem with your device... or maybe you have installed some bad software app (like a task killer for example) that is causing it to totally crash and turn off.
As for how the power button works and sleep/standby verses deep sleep...
Normally, if the device is up and running, a short tap on the power button will just turn off the screen backlighting. However, you can change it to always go into deep sleep instead if you want in the Settings options.
If you hold the power button for a couple of seconds it will pop up a box with options for Deep sleep, Reboot, or Power off.
If you hold the power button for tens seconds it will reset and totally turn off the device.
What Deep sleep does is not only turn off the screen, but also throttle down the CPU to a very slow speed to use far less power (it also disables Notifications because the CPU is running far to slow to handle that extra stuff, so no Alarms will work either).
As a side note, there are other options in Settings for if/when it should turn off Wi-fi or the 3G Stick when the screen turns off.