not a good procedure when two individuals are in the situation of both shooting at an animal. The practice most often results in decreased accuracy for both "shooters". Usually more accurate results are achieved if only one individual starts the shooting, then, if necessary the other individual can start.
HOWEVER when the shooting starts, neither individual should move from their positions without first opening their bolts - pay constant attention to both the animal being shot at and the position(s) of other individuals in the party - and - if three individuals are present - no more than two should be shooting and the third individual act as a "control" monitoring the shooting of the two individuals and the actions of the animal being shot.
"Now or never", by its self, is never a "good reason" to start shooting.
See Mike - I am TEACHABLE!