I am not disputing what is advertised and what others experienced with their battery powered systems, but personally I never met a machine that lived up to those claims. The key word you hit upon, Cory5412 - "Light-Usage."
Before I retired from the school system, schools bought laptops thinking that students can use them non-stop 9AM - 3PM, 6 straight hours without charging, as advertised. But the truth is, they only lasted 3 hours or less. OK, they were doing a lot more than just writing assignments. They had to accessed the school wireless network, the internet, up/download data/assignments and do multimedia presentations. The Computer, Science and other after school clubs also did things with the laptops from the hours of 3PM to 5PM - adding 2 more hours. Many schools had to double their orders so that students can have a morning laptop and an afternoon laptop, which defeated the purpose of the 1 laptop per child mantra schools had.
Plus improper charging of the laptop's batteries killed the battery's life in many laptops so that they could only function for a single 45 minute period.
Personally, I'm not one of those light laptop users. I run several apps at the same time and constantly access the hard drive or network. For me, battery life is in the best of conditions is a couple of hours. I'm pretty sure that if I get several nuclear pacemaker batteries to make a battery pac for a laptop, though such batteries are rated for 10+ years, I'd probably run it down in less than a month.