Well, this isn't something you hear every day. According to both the folks at WPCentral and XDA-developers, Nokia Lumia 800 (sibling to the US Lumia 900) users in Singapore received a recent OS update has nearly tripled the device's battery life. If true, that would likely not only prove that software can make a big difference in battery life, but also set a new standard for both Windows Phone and Android smartphone battery life.
WPCentral provided some qualitative data with their triple battery life claim, which could just be interpreted as a symptom of poor base battery life. However, the good people of XDA-developers provided a more quantified measurement that suggest otherwise. According to their information, the standby battery discharge has been reduced to about 80mA from 150m, which would suggest close to double the previous battery life. Again, I'm not sure what a good standby discharge score is, but this sounds fairly low to me. No one really knows how the improvement was achieved, but it is suspected that better management of screen brightness is a contributing factor.
Although this specific update only helps Lumia 800 owners, the changes do have the potential to impact all Windows Phone devices if the problem fixed turns out to be one with the core os. At the very least, anyone who has or plans on getting a Lumia 900 might also want to take a look at their available updates, but if this turns out to be a new Windows Phone 7 improvement, it could be quite a big deal. More likely than not this is just a fluke, but we can always hope for battery life double that which we enjoy today.[WPCentral | XDA-Developers]