His reasoning applied to the length of Broadway plays, or the length of political terms, is valid because such events have been going on for a long time, there

His reasoning applied to the length of Broadway plays, or the length of political terms, is valid because such events have been going on for a long time, there have been multiple occurrences and they have a naturally limited length. Many have already ended, so it can be considered that we are in a "steady state" and statistical considerations about the events can be made. In the case of singular events however like the extinction of the Human species there is no such assumption. However when he uses the "95% rule" he implicitly assumes a normal distribution of events. That render his conclusion invalid due to use of an invalid starting hypothesis. In the case of the Berlin wall, he was just lucky.