Each campaign has it's own duration. When the timer expires there's usually a couple hours that go by before the leaderboards are back up. During this time, factions might try to take as many keeps/outposts/resources as they can to give their faction more points when the campaign starts.
I've only played when a campaign was being reset once before so this information might not be 100% correct.
Planchard - V14 Templar Healer DC Rank 24 (Retired)
Leggo Mayne- V16 Stamina DK DC Rank 27
When do campaigns reset? Also if the timer says done on the campain what is the point in going into the que and taking stuff?
When a campaign ends and resets ONLY the leader board and score resets. The actual map remains the same, so there is never a reason not to do anything or a reason to give up or wait for a map reset. It is a persistant world like Darkaage of Camelot or like Planet Side 2. it is very different than games like GW2 where they reset everything.
Actually winning the campaign is just a small after thought bonus. The real reward comes from controlling the map for its current bonuses. Winning on the map can be done at anytime, regardless of the campaign time or score. most people prefer this system because you never feel like your wasting anything that can be reset, Your actions stand until enemt players take action to change it. There is also no giving up and waiting for a reset since it never happens and really no reason to since controlling the map is teh reward and not "winning with the end score"