I get by easily for 2 days:
Wifi on from about 18:00 untill 08:00. (auto sync on)
2G, 3G, HSDPA for the rest of the day (auto sync off)
I listen to music (local files) for about 2 hours a day during commute time, while I read/write mail/google+
I don't call a lot. about 30 minutes a month.