Gentoo was the primary source of heating for my living quarters back in the early 2000s. My tower was highly constrained on memory, and I was on a relentless quest to pare out any modules or dependencies I wasn't actually using. Performance gains were primarily from being able to stay out of slow HDD swap space memory. I doubt there were any gains once amortizing the compilation times, but I ran my compile batches at night, and they kept me nice and warm.