all battery life and battery percharge are all Estimated !!!
I have updated, and it looks great so far 67% 4:49, same percentage used to be 2:15
accourding someone here so wanted to be Apple expert, you will never need to update your OS X, as it shipped "perfect", all you need to do is change every single part of your hardware and software until you get it right OR unitl you get "sicked".
accourding to Apple official and REAL APPLE Expert, they will always advise you to update to the latest software updates.
which one you taking is up to you, but if you don't update, you will not able to find out what is really wrong with your system, as if that problem is really exclusived to your system's problem.