I have been getting the Low Battery Audio Warning & Icon for over 1 hour now while listening to the internet radio. Is there a way to set the warnings to a much lower level?
N800

Interesting, my N800 shuts down about 5 minutes after a battery alert (after about 3 hours of opperation). I don't believe that level is adjustable. Sounds like that is a characteristic of your particular battery. Can you try another battery to see if it behaves differently?

Oh, one other thing. If while you are playing your music your backlight turns off there will be much less current drain from the battery and you will be able to continue a longer time until shutdown.

my n800, if on online wideo will shutdown in about 5 mins. after the warning, and 20 mins if on online radio with screen off. It's probably very much up to the particular battery, os version, temperature and so on.