It depends on the number of particpants and the manager ussually add the allocation for all the campaign but sometimes not, so i think you must stay because many campaign will kick you out if dont post any report anymore, you will regret it because all you have done and you get nothing.
That is true there are campaigns wherein not posting for a certain number of weeks after participating would cause you to be disqualified from the bounty. I have seen those kinds of rules and I make sure that when I join those kinds of campaigns I set some kind of reminder that would remiinid me to work their campaign on that particular day or days. Otherwise I will be disqualified and forfeited my participation on that campaign.