A time table - Physics 101, Lecture room 2B, 9am every monday.

Movie schedules. Movie X shows every day this week at 17:00, 20:30 and 23:00

A store list with their opening and closing times

An example I've actually used - storing the start time and end time of daily jobs

I can certanly do that with a datetime (and I have done it), but then I have to set some form of meaningless date.

Is it the norm? No. Are there cases where it's useful? Absolutely.

I would never store duration as a time. That's asking for nasty maths. Store is as a number of hours/minutes/seconds, depending on the granularity required.