Wow I was gonna ask this same exact question.
How about putting a LINE next to an answer. So you know if it is RED and/or SHORT that the question was answered in less than a minute. or if it’s X pixels and blue that it took x minutes/hours etc.
this way it can still keep the “Zen” /simple awesome look (no numbers or extra text) and yet tell us about the time.
or a line with circles on it in every x th pixel (distance/inch) and each circle is 1/4 hour or 1 day etc. or the first circle is 15 min. and the second is an hour , day, week etc.
so if it is a Filled circle, you’d know that you made/missed the mark (even a point system for fast answers? )
I hope this wasn’t confusing, think about a timeline (a straight line with Empty circles every x inches) anyways….gahhhh