The staff have been so wish-washy about this title topic.
In the past they've said you can leave to sell/zone if you're able to return before the mob spawns and keep it down without delay.
Then I just heard braknar and sirken talking on sirken's latest stream about outdoor spawns and they said you can only really camp 1 outdoor spawn. If you leave it you're no longer camping it.
so idk, just don't be a jerk.
Play Nice!