Given that theory, we never see people over about 120 because...?
So even if there is no upper limit to the human lifespan, and mortality doesn't increase after 100, it would be very rare to see people older than 120.
1. there are few, as the world has 7billion++ people today and 120 years ago it was around 1 billion. You certainly are not going to meet them.
2. Someone that is still sane past 100 years will not care about bragging his age to us younglings.
3. Finally, we don't ask these people their age. And when we do, we don't believe the answer.
There are some histories of people with more than a hundred year. Li Ching Yuen[1] was a Chinese herbalist that lived more than 250 years.
Ah! Clearly the human age register is only 8 bits and when it overflowed his body crashed.
Try to plan ahead a little better when designing human 2.0 God!
This skepticism is borne from living a life of being gaslighted and conned in a high-demand religion, and breaking away. I don't doubt there are occasionally a few long-tail events that skepticism causes one to miss its reality, but as far as seeking mysticism or a hidden reality (hidden by whatever underlying power, be it gods or billionaires, pick your poison) I find life much less stressful and more fulfilling with a healthy dose of skepticism.
That kind of statement begs for a story.
Just in case you want to try it out for yourself.