My initial thoughts are that if you have clear goals for your teams, they will perform according to those measures you set. Consider what processes you are using as well? To maintain creativity you still need to have a process that encourages completion. A third idea is to have at least one or two facilitators in your team that are responsible for assuring you are meeting the goals and expectations for the team. It could be a team leader or it can be a role that changes from project to project and that all members of the team have skills in facilitating the team's approach.