We had a maximum accrual of 240 hours (30 days). For a while, there was a policy that managers should start to encourage you to take vacation once you accrued half that. They got increasingly more insistent the closer you got to the maximum. That combatted the pressure to put off your time off to get a project done faster.
I even had one manager who gave employees the choice between a cash bonus and paid vacation time. It was clear that we not only had permission, but were encouraged to take the time off. I picked the vacation time. The same manager had an informal policy that if you came in to work on a weekend day as part of the final push before a deadline, you got an “off the books” vacation day as a thank you.