Forum Discussion
Iteration Fatigue!
Aside from comments that are only about fixing typos and similar errors, all comments should be considered "suggestions." Just because one reviewer wants something said or done a certain way doesn't mean others will agree.
If possible, establish one person who has "final say." After collecting comments from the group, that person should go through the review file and indicate which comments to implement. This helps solve conflicts before you make the edits. And, hopefully, it'll help you avoid re-revising the same piece.
If there just isn't one person who has that power, it might help to set up a meeting to discuss comments and decide which suggestions to use.
Be sure to stress at the start of each review cycle what people should be looking for -- and what has already been approved (and will, therefore, cost extra to revise). That's especially important for audio and video scripts.