I googled that recently, and it sounds like:

They don't get reused.

There are about 70 years left.

The government is punting the problem to future people and there's no solution yet.

They are absolutely reused. I know this because mine was previously issued to a man who died in the late 50's.

I've heard people say that, but the SSA's FAQ says otherwise:

"Q20: Are Social Security numbers reused after a person dies?

A: No. We do not reassign a Social Security number (SSN) after the number holder's death."

https://www.ssa.gov/history/hfaq.html

It should be an error then, it isn't reused according to https://en.wikipedia.org/wiki/Social_Security_number#Exhaust...

There’s less actually. Each state has its own unique 3 digit prefix.

SSA implemented randomization in 2011 to remove that artificial constraint.

https://www.ssa.gov/employer/randomizationfaqs.html

I don't think that's true anymore. I was born in the same state as my wife and we have different 3-digit prefixes. But I agree that there are some rules about the different parts of the number that further constrain the theoretical one billion limit.

You can compare against the Social Security Death Master File of SSNs for those who are already dead.

https://www.ssa.gov/dataexchange/request_dmf.html