Bad battery life is not an inherent property of Linux. If it were, you wouldn't see so many "smart devices" running flavors of Linux. With respect to laptops,

Bad battery life is not an inherent property of Linux. If it were, you wouldn't see so many "smart devices" running flavors of Linux. With respect to laptops, there aren't enough people looking at every SKU, of every manufacturer, and then translating the possible power state combinations of each bus and link and adapter into the config tools preferred by this-or-that single distro. It would require be a massive, more-thankless-than-average undertaking. As a result, the median laptop is not optimized for battery life out of the box, even for distros that do try (to say nothing for those like Arch that intentionally eschew making choices for you). With some tools that allow self-tuning, it's not difficult to get 8-10 hours of battery life on the newest x86 platforms (or more on ARM laptops). However, it isn't done for you. It is an area that desktop Linux needs to invest in improving on behalf of the majority of people, who are less inclined to experiment and tweak.