I'm calling ********. I support Dells at work and they have the absolute worst batteries I have ever seen. Every single one of the D620 and 630 notebooks coming off warranty have flat batteries and most failed a year and a half into the three-year hardware cycle. Check the Dell website and you'll see the same thing from thousands of customer reviews. I have zero experience with Lenovo, but you're totally wrong about Dell.
we go through hundreds of Dells in a year in a similar 3 year rotation. The batteries make it a year or so depending on use (or lack thereof).