|It's not very open (or closed?)|
As I thought more about this, of course, my thoughts turned to tenure-track professors. By comparison, tenure seems like an infinite window. Even then, it's worth recognizing that funding situations change; nobody can predict the funding picture in 10 years for even the most august state-funded universities.
By comparison, my father has worked for the same private company for over 30 years. I simply cannot imagine the concept of near-lifetime employment. It's my assumption that this option is closed to most chemists of my generation.
Best wishes to all of us.