In a developed country a newborn female is expected to die die at aroudn 79, according to insurance tables. When she reaches her 79th birthday, her life expectancy, assuming she is in typical health, is another 10 years. At the age of 90 , she should have another 4,7 years to go. At the age of 100, 2.5 years. At the age of 119 if she miraculously lives that long, she should have about nine months left.Let's say a project is expected to terminate in 79 days, the same expectation in days as the newborn female has in years. On the 79th , if the project is not finished, it will be expected to take another 25 days to complete. But on the 90th day, if the project is still not completed, it should have about 58 days to go. On the 100th, it should have 89 days to go. On the 119th, it should have an extra 149 days. On day 600, if the project is not done, you will be expected to need extra 1590 days. As you see, the longer you wait, the longer you will be expected to wait.
That is remind's me of Tommi Liimatta's comic, where someone waiting at the restaurant notices, that the probability that one waited, will arrive just now increases steadily, until it suddenly starts to to decrease rapidly. So it probably will tell you something about yourself, if you are still waiting after 20 minutes.