"My conclusion is based on 57 years of observing human nature. If you give someone an inch, they'll endeavor to take as much of that inch as possible and often more. For example, when the speed limit on the Interstate was 55 MPH, people routinely traveled at 65 to 70 MPH. Now that the speed limit is set at 70 MPH, they want to drive at 80 MPH or above. If a diver looks at his computer and it says he has XX minutes left until NDL is reached, it is simply human nature to try to take all that is given. When you consider that one diver's DCS threshold will differ from that of another, diving right up to the NDL over and over could be asking for trouble. Sooner or later, the law of averages will catch up to you.