I knew a guy at work that regularly took 1 to 2 “sick” days a month. This went on and on for years. When he left (fired) he still had 240 hours (6 weeks) of vacation time which was the max for each year.
That type of situation is why a lot of companies have shifted to a “time bank” or PTO (paid time off) policy, which lumps sick leave and vacation into a single pool. I don’t get paid sick leave, per se, I get PTO, which applies to any reason I’d be out of office - if I avoid taking sick days I get more vacation, if I can’t I get less vacation.
At a friends old employer the situation was reversed. Vacation days expired but sick days did not.
He used vacation days for sick days and saved his sick days. He had a bunch of them when he was laid off and they had to pay him for them.