Hours – (IT Scheduling)

I have a staff of three (plus myself) in a small software company. I have always set the hours for the technicians, balancing their preferences with our needs. I have a new tech that is requesting different hours on Tues and Thurs than the other work days. I have suggested that it would be best to have the same hours every day, but I also want to be as flexible as possible. Critical support hours are being covered, but I don’t want to start a scenario where the other techs ask for equally changing hours to the point that i don’t know who is supposed to be in at any given time.

Be flexible or crack the whip?