[uptown]

According to the site - for the battery-powered version:

"6 AA Energizer Ultimate Lithium batteries Long-life batteries designed for multi-year operation"

and for the wired version:

"3 AA Energizer Ultimate Lithium backup batteries Long-life backup batteries designed for multi-year operation"

I suppose it depends how much you use its features like lighting-up your hallway, but that's more-than reasonable in my opinion.

[raverbashing]

I really wished they had innovated in that sense

For example with a wireless energy transmitter (it doesn't need to be too powerful).

Or "solar powered" with a good set of (rechargeable) batteries.