If you activate a second Rage whilst the first one is still active you still get a crash when the first one runs out. This wasn't the case a while ago ( I4 or I5 perhaps or earlier? ).
So if you Stack Rage you end up wasting 10 seconds of the second rage because you are in the crash of the first.
In order to perma-Rage you need 3 recharges or 2 recharges and Hasten.
IIRC
1 recharge and Hasten will give you between 0-20 seconds of Ragelessness.
2 recharges and Hasten will give you up between 0-20 seconds of stacking Rage, however a new Rage will always be ready before the end of the crash period.
@Unthing ... Mostly on Union.
Ahhh... I see, so it doesnt get rid of the downtime, it just makes it available again straight away.
Thanks for that! 
thats got to be the funniest and cutest avater ive ever seen tryin!
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
Thanks!
I think i've seen it elsewhere on here, but just for clarity - if you have 2 recharge reduction SOs (or hasten) in rage, you can activate it again before the crash comes? postponing it, so to speak, so you just get one crash at the end?