I've seen it done as a "maximum accrued vacation time" policy. Once you got 30 days accrued, you had to book enough time off to reduce it to less than 30 days w

I've seen it done as a "maximum accrued vacation time" policy. Once you got 30 days accrued, you had to book enough time off to reduce it to less than 30 days within the next three months. Everybody hated that too. Being forced to take time off when you didn't particularly want to, and not being able to "save up" enough vacation for a really good ling trip away... And, of course, those rules were regularly "bent" when it suited management, but rigidly enforced otherwise... (We typically accrue 20 days per year here in .au, so that pretty much means after 18 months, if you haven't taken any vacation at all yet, you need to take at least a week off in the next three months, and a week off every three months thereafter.)