I have ver 6.0 and i cant stand this... off the top of my i head i would try ad modify firefox.exe with a hex editor and change the ver# to somethig crazy high like: 99.3.6 so you will always be ahead of the update... I tried making a blank updater.exe but it spawns from the appdata via firefox (like a worm) very frustrating im considering switching browsers, or downgrading to 3.6... Ill make a post that hacks/solves this since mozilla thinks they push us into updating for statistics and profit.... yeah right

Under options -> advanced -> update

Ok i solved this, just delete updater.exe from program files than navigate to %appdata%\local\Mozilla\Firefox\Mozilla Firefox\updates rename the folder "0" to anything other than 0. and your all good.