[amanmann]

I got a new G4 1.33 ibook and it's the only computer i have here so i use it as a desktop replacement too. I need to know whether it is better to keep the charger plugged in while i work or is it advisable to charge that battery and then let it discharge.
But I guess there is a finite life of the battery life cycles. Mine has gone through 56 cycles already and my fully charged battery gives upto 4:30 hours backup.

Any suggestions.

[volcano]

As suggested by Apple, you should charge and discharge your battery completely about once every month if possible. This is also referred to as 'calibrating' your battery - where you charge it up until your battery is full, and then use it continually without charging it until the computer falls asleep, followed by a full charge once again.

You can learn more at: http://www.apple.com/batteries