Here is the word from Cesar on new zunes battery life with the wireless turned off.

Zune 4GB and Zune 8GB
Audio: up to 24 hours
Video: up to 4 hours
Tested Using: 128kbps .wma tracks

Zune 80
Audio: up to 30 hours
Video: up to 4 hours
Tested Using: 500kbps .wmv videos