How does a half standard-rate turn's duration change based on the degrees turned?

The correct understanding of how a half standard-rate turn's duration changes based on the degrees turned is that longer angles indeed take a longer time to complete. A standard-rate turn is defined as a turn at a rate of 3 degrees per second, which means a half standard-rate turn, being half of this rate, progresses at 1.5 degrees per second.

For angles that are larger, it requires more time to execute the turn because the time taken to complete the turn is directly proportional to the angle being turned. For example, if you are turning through 90 degrees, it would take 60 seconds (6 minutes) for a half standard-rate turn. In contrast, a turn through a smaller angle, such as 30 degrees, would take less time, specifically 20 seconds for completion.

Thus, the relationship of duration and angle is linear; as the angle increases, the duration of the turn lengthens accordingly.