[vcxy]

The heuristic is that the average of an interval is the middle. If you know nothing about it other than you're at some point on the time interval, assuming you're at the middle time is a good prior.

When you know more, you certainly should adjust. For the job example, you might think "how long have I usually stayed jobs that have lasted least two months?", "how long do people usually stay in jobs if they make it through the first two months?". Generally speaking, Bayes' theorem is the technical answer to "how do you adjust". Not that I ever actually do that...but I think it's the technically correct answer.