Thanks to all who replied for confirming my beliefs regarding this matter. The issue came up while I was parked next to another aircraft during a run-up at night and I turned the strobes off as a courtesy to the pilot next to me. My instructor (I was getting a Cirrus checkout at the time) insisted that I turn them back on because the FARs said they must be on at all times. It’s now clear that I have the authority as PIC to turn them off if I feel it necessary. Thanks again!