I already pointed out that the extremes of the distribution are irrelevant, the average matters. Basic statistics, you failed at it.
If I had time on my hand I would dig out some old empirical evolutionary economics papers or search for the data myself but I am pretty sure that the average lifespan of publicly traded companies is less than half a century.
The company I use to work for is publicly traded and is 154 years old. Most of the major automakers are around a century old and they're publicly traded. There are a lot of publicly traded companies that are past the half century mark. Proctor & Gamble, Kroger and Fifth-Third Bank (which I worked for) are three right here in Cincinnati right off the top of my head.
So, once again, it's not out of the realm of possibility for Offenhouse to believe that a bank and law firm he used might have survived. Especially given the fact that he was kept in an informational vacuum.