Unlimited vacation days are a trap. And a misnomer. If I never show up to work because I am “on vacation,” I’ll be fired. If I don’t show up half the time, I’ll be fired. If I take 30 days off, I may very well be fired.
There is absolutely a limit on “unlimited” vacation days; it’s just that the jerk employers who maintain that unlimited vacation is a benefit won’t tell their employees what that limit is.