Back in the 1990s I worked at an investment bank that offered a paid 3 month sabbatical after 10 years of service, and then every 5 years afterwards. I don't quite remember the specifics but that was the gist of it. This was on top of normal PTO. They didn't tell you what to do with the time, but encouraged doing some deliberate personal growth.
This is standard in Australia (Long Service Leave). The exact terms change from state to state but usually similar to what you have described (e.g. 2 months after the first 10 years, then 1 month every 5 years).
It was a rather uncommon benefit at the time.