There is well known trick among programmers, to just advance the progress bar independently of how much of a progress is actually being made. Then when all the tasks are dane, just quickly skip to 100%.The problem with that approach is that when you advance the progress bar many times during the period in which there was almost no progress being done, then your progress bar is almost at 100% but you still have a lot of tasks to process. Of course this ends in stucking the progres bar at 99% ;)