Discretion should not be used on a regular basis. There is a Notice to AOC holders somewhere that suggests that if a particular roster goes into discretion more than 30% of the time (I think) it is deemed unreasonable. CAP371 also states that published rosters should have reasonable block and turnround times.
At the end of the day if you are working hard and asked to go into discretion just refuse; but give crewing a reasonable time to find someone else.
At the end of the day contact your FOI ( he might even be reading this thread)
