I get that, this sort of test is often hard to do in the real world. How about the following test that might make you challenge yourself on how good long term acoustic memory is.
Do the classic mp3 vs flac test with a software tool that gives instant switching, e.g. foobar, use headphones or speakers, whatever works for you, use the highest mp3 bitrate you can pass the test with. When you are comfortable with this move on to the next stage.
Foobar offers 4 buttons to press to work out what is what, A, B, X & Y. For the next stage before you press any of them mute, press the button then un-mute. You can do this 3 button press as fast as you like. Can you still pass the test?
For the next stage leave mute on for 60 seconds across the switch. Can you still pass the test?
The beauty of this test is you know no cheating is going on as you are in total control of it, and you know an audible difference that you can determine blind exists, and continues to exist through the test, the only thing that changes is the long term memory part.