If you're having issues with battery when you're not plugged in, I can highly recommend Turbo Boost Switcher (http://tbswitcher.rugarciap.com/) to disable Intel turbo boost. I've noticed no slowdown or performance decrease, but my fans spin up MUCH less often and my battery lasts a couple hours more.

I suppose it goes to show just how badly Intel has screwed up in recent years -- so much development went into this "Turbo Boost" feature that heats up processors hugely under any sustained workload in a way that no laptop can properly keep up with. In certain cases it could make sense ("my project takes 20 seconds to compile, and then the processor basically shuts off") but I routinely end up pegging the CPU at max for 10s of minutes at a time for huge compilations, and the minute the fans spin up I know that Turbo Boost is about to thermal throttle my CPU into oblivion.