If the game allows it, there's no "rules". I get annoyed by people who cry about pulling early, because no one owns the mark. Anyone can pull it whether they're the first to find it or they arrived after everyone else. Shouting pulling times is only inviting someone to "pull early" anyway, and honestly, if you have enough people there, just pull the damn thing. If you have to wait till 9:15 for some late arrivals, might as well wait till 10:00 for even more. As for resetting, like I said, if the game allows it, there's no rule against it. Some may say it's discourteous, but then I could argue it's discourteous to not wait for another 100 people to arrive when you pulled the mob when your party was all there.