Installing a version of Android without Google Play Services running constantly in the background effectively doubles handset battery life in my experience. Disabling radios can do that again if the device is rarely used.
Turns out stateful firewalls aren't just a security factor on mobile internet connections.
I did have an experience with my phone being suddenly used by random internet users. I had ampache running on my n900 (maemo/debian-based) and somebody found it on the internet and started streaming my music. :D I had a higher-than-normal amount of battery usage for a few days so I decided to see what's using it and discovered that my music was being played and downloaded.