Today, to do a test I've loaded the battery full again.

I've made some SIP calls, had a MSN conversation and the battery still shows all blocks!...

I'm disconnecting wifi and put msn/skype/sip offline every time I lock my screen again.

at same time yesterday with wifi on and the chat/voip accounts logged in all time it was down to 1 or 2 blocks already.

CONCLUSION:
either way. setting this manually every time is not really a option.
can't there be some build in option that closes the wifi connection and switches to 3g or even 2G to save bat. when 'locking the screen' and optionally log off msn/skype? :-)

PS: I've basic knowledge of c++ and will look into programming for n900 soon if I have more time, but I guess i will have to start with hello screen as I have no knowledge of linux and needed reps etc etc. haha