Thanks, That's a good question, I'm not completely sure yet actually. Usually battery life isn't too much of an issue as there's always electric plugs around where I spend my time.

Something that can have a simple multiple monitors setup / hook to the TV setup. Something that's not overheating, but that would be powerful enough (not sure if those 2 are compatible!) to compile C++ programs full of templates. (i.e. good multicore setup, 16+ gb of RAM, and a large enough SSD), and a 14 or 15 inch monitor

These days though I'm wondering if I should simply get a desktop and a tablet for everyday browsing. The reason I favor laptops is because I'm assuming Linux support of the different drivers there would be better than a custom made desktop, I might be wrong there! I'll do more research as my w520 gets obsolete, but after easily replacing its DVD drive bay with a second SSD, and disabling the Nvidia GPU, I get a good enough experience right now.