Honestly the wisdom I have has just been playing around with benchmark.js on V8 and noticing the Chrome team doesn't do as they claim (although latest Chrome Canary we saw major improvements), while FireFox is a different beast. You've probably done about just as much of this as me.

What we found was that every function call in javascript significantly decreased performance (even if it did nothing) at a quazi logarithmic rate. So on a theoretical level if you're able to reuse function results that are deterministic you can save a ton of overhead. However IDK how micro-optimizing you want to get as it can sacrifice code legibility.

Would love to chat more if you have time, I'll see if I can find your email and send you a message. Mine is (no spaces): a q u i v a @ google's email provider.