Hi Zimmy. My DX used to go for about 3 or so weeks between charges with 3G turned on. In recent times before I got the PPW it would last two or three days. I turned off 3G and it'd last a couple of weeks.
The DX is nearly 3 years old now, so presumably the battery in it has a finite life. Hopefully I'll get longer service from the PPW. Currently I'm seeing about 2 weeks between charges. However, that's not an issue.
I have a charger connected by the bedside table so it's not a problem to connect it any time I feel like it, to ensure that it's fully charged.