Apparently Jim Treybig (Tandem founder) was big on people. He came from HP, and brought over the HP (at the time) way. I think a lot of employees even got 6 week paid sabbaticals every 4 years.
Yes, all Tandem full-time employees got paid sabbaticals. And stock options.
My partner joined Tandem 2 years after me, so our eligibility for sabbaticals was out of sync. One of us would have to defer our next sabbatical for 2 years to get us in sync. Instead, we both took off together for 6 weeks every two years, using time off without pay when it wasn't our turn for a paid vacation. We took a lot of overseas trips.