The trick to getting the job manager to work with this is
all the characters have to be on a task - no one can be waiting for something to doall the characters for a given time task have to be at the same level of time left - so if you have a bunch on 4 hour tasks, all have to be 24 minutes or less left
I use the 4 hour tasks most of the time too - 8 hours for late night/overnight & occasional 12 hours when I know I'm going to be really busy.
I have to confess that I almost never use the 24 hour task & have no idea what the timeframe is for the free speed up.