I did a first little test (a 5 min countdown):
The accuracy is actually better than with the clock. In a 5 minute countdown, the extension only loses a little more than 1 second compared to a chronometer.
Of course, that’s not the purpose of your extension, it was just a small test to see what the extension can be used for.
If the .AfterDelay event is not triggered regularly (excessively often), the delay seems to be quite precise.