All tested on Siemens CX65 with its standart battery (but we might also assume this information for our E/EL71, I think it's not so different), although I don't know for how much time everything was tested:

The phone is switched off - 35 µA
The phone is switched on, but without any operations been done - 1.1 mA
Screensaver mode (any) - 1.1÷1.2 mA

Backlight 10% - 30 mA
Backlight 20% - 40 mA
Backlight 30% - 55 mA
Backlight 40% - 70 mA
Backlight 50% - 80 mA
Backlight 60% - 90 mA
Backlight 70% - 110 mA
Backlight 80% - 120 mA
Backlight 90% - 135 mA
Backlight 100% - 135 mA
(all other results are given for switched off backlight profile)

Talk via phone - 120÷220 mA
Playing mono-MID melody (min/max volume) - 70/190 mA
Playing MID melody (min/max volume) - 80/170 mA
Vibration - 80 mA
Dynamic Light - ~40 mA (we can assume this as our yellow indicator for new inbox)
Camera viewfinder - 75 mA
Camera shot - 100 mA
Video recording - ~160 mA
Voice recording - 55 mA
Video pkeying - 150 mA
Java performing - 60÷70 mA
Java in awaiting - 4.5 mA
Cable connected to the phone - 32 mA
IrDA - 0.2 mA (not important for our handsets)

Therefore this guy draw some conclusions, how to increase the one-battery-operating-time of the handset
- lower down the backlight till min comfortable parameter (you also noted it)
- switch off the dynamic light (in our case it doesn't matter, as the indicator starts blinking only when a new message/call/date is income)
- the "Energy saving" mode does not save anything, so there's no advantage in using it instead of screeensaver (but in Siemens S55 it really helped)
- if a cable is without the extra-charging, it's better to disconnect it, if not used
- Java-machine is correctly built and consume the power only when nessesary (as for E/EL71 I can't confirm this statement)

This values and a conclusion was given by jagr. Translated by PaulS

Also I've seen some article long ago, I don't remember where actually, but the main point is that everything should be switched off for longer operating time. The switched on GPRS and Bluetooth requires a lot of power, especially if you're in some Underground or where network coverage is quite low.

And other thing (in e71! I don't know what about el71). As we can see there is no automatically switching off backlight with keyboard block. Just install patch "Disable message "Keys blocked" and enjoy it. Pressing # will block keys and disable backlight.
So I use 15sec, it's not a problem.

Yes, when i had the cable, soon i'll made it extra performance handset, with minimum power consume

Talk via phone - 120÷220 mA
Playing mono-MID melody (min/max volume) - 70/190 mA
Playing MID melody (min/max volume) - 80/170 mA

Is it logic, to use handsfree (to make a call, listen audio files), to get more power saving, or it may add consuming energy, transferring audio file electricity stream to headset speaker?

But couple days ago, my friend found non-original one, it's for AL21, i hope it's compatible with EL71, if it's not, i will just modify it

It's quite good for non original spare, it's just less "bass" tone, compared with my original S75 original HF.

Recognized as "HHS-150" on EL71, it only cost Rp. 25.000,- converted to euro, then it's only 1.7 euros