Wayne Nash offers sound advice on reducing drilling time...and shares a recent adventure.
For instance: Do you fuel the rig on the way to the job or on the way back? If you stop to fuel on the way to the job, you have just increased your critical path time by 15 minutes to 20 minutes for no reason. If the rig left the yard full, you could save the time. Fuel up on the way in - it is something that needs to be done, but it doesn't interfere with drilling. It is a checklist item. Do it outside your critical path.