Hopefully you learned the lesson: just because someone for the lack of a better advice tells you "hard reset" you should NOT do it! Makes mostly NEVER any sense to 'just reset' the phone or computer!
Either it is something wrong with YOUR specific phone, or you can try to set the Stand By Mode while on External Power to NEVER, turn off backlight to 1min
at least with these settings my phone won't change!
Another try might be setting on external power to 2 min for standby and 1 mon for Turn Off backlight.
Usually the change from Battery 1 min backlight to 30sec. happens when the phone is connected to the ac and then taken off ac.
But again, I solved that on MY phone with the settings:
Battery: 1 min for backlight
2 min for standby
On External Power: 1 min for backlight
NEVER for standby
and it says that way until battery dies and ac on or off does also not matter. It just stays that way. Give it a try.... it much less painful then a senseless hard reset
«.·°·. Michael the Mage .·°·.»
<<<Of Peace, always!>>>>