Yes, I use autodisconnect and the phone is on the 2G network almost all the time. I dont use much wifi as I have dataplan (is 3 eur/month (unlimited 384 kbps) cheap or what?), and emails are not checked. More specs:

- Wifi search interval set to "never"
- GPS disabled
- Few widgets on the desktop (weather&stepcounter)
- Bluetooth disabled

Is there anything to improve?

Where did you change that wifi transmit power?