You get 400k XP worth of enlightenment pool once every 24h. Some post claimed it happens at midnight, some say it's 24h after the last one, but neither seem to be true now. The 400k is credited in one go so there's no way someone can burn it in a minute or two. It is account wide which means you might use up most of it one another toon and leave little or nothing for the next character.
Relogging should not empty the pool, even if it envolves a non-veteran alt. However on PTS there is still a bug which resets the pool to zero if you log in with a toon for the first time evet since patch.
Zoning should not effect the pool either. However the game likes to spam the on-screen message about you're being enlightened after relog or zoning. This does not mean you got enlightenment multiple time, just indicates that you still have some points left in your pool.
So I am not sure what is going on here because ZOS has been very vague with the enlightenment roll out...
So I was leveling a toon that just hit vr1. A few minutes later the heavens tell me "You are Enlightened" and my CP bar flashes. This new vr1 toon is not geared so I log into my other one to grind a quick 100k for the CP. The second toon has no buff and the CP bar says 143k/400k. Weird? So I log back into my ungeared toon and his CP bar also now says 0k/400k and there is NO BUFF.
I'm sure what the issue is, but be careful relogging or switching toons until ZOS gives us more information on what the actual enlightenment process/buff entails.