"What's your favourite thing about this movie?" "That it's exactly ninety minutes long."

With the 'long' coming at the precise moment the runtime tips over from 1:29:59.

But it totally depends on why you need a piece of media (or even art).

At the most extreme end, your runtime is fixed. Eg a specific song in a musical might have to last a certain minimum time, so that the crew in the background can quickly change the set.

Or think of background music in a game, or even in a bar. They have to be on for as long as it takes, and shouldn't loop too often.