I have a wireless kit for the intuos, unfortunately I can't tell you about the longevity of the battery as I have not used it consistently enough to figure out how long the battery lasts - however you do get an extra battery within the wireless kit and if you have an intuos, it already has a battery so...you get two batteries in total.
The wireless signal is fine, I've drawn from my bed (4 feet? from my desk) before using the wireless kit with no lag at all - and I doubt you're going to be drawing from a distance further than that considering you still kinda need to be looking at what you're doing on the monitor.
To ''install' the wireless kit, you have to open a tab under the intuos, pull out this usb-looking thing, put in the wireless kit, and voila - cordless tablet. however, this might just be me, but you can't use the cord and the wireless kit at the same time. It's not that it stops you from doing so, but if you have driver backups and your driver fails, those backups are NOT going to work while you're using both the cord and kit.
I'd only recommend it if you travel a lot. I only got the wireless kit because it became a hassle to constantly disconnect and reconnect my tablet cord to my desktop every time I went on a trip or took my tablet to school. Other than that, I don't use it much.