retired guns

Judges, when do you instruct your throwers to retire and why? For example, throw and then retire soon after the bird hits the ground like at this field trial: Or throw, stand motionless, and wait to retire when the working dog is released for the first mark? Thanks.

From page 30 of the Field Trial Rules and Standard Procedure for Retrievers: "Retired Guns and throwers should be concealed by a blind that provides complete coverage, adequate space, and natural camouflage to conceal the distinctive shape of the blind ... No blinds shall be placed in the field...