Well there’s a few factors that affect this. What level employee are you? Managers may have a harder time taking off if they cannot get the appropriate person to hold the reins while they’re away. A lower “grunt” may have an easier time if their work is easy for others to assist with. Personal time is usually always approved weeks if not months in advance. Emergency days such as a dying family member is always allowed, and of course you can’t plan for these in advance. A robust system is the best way to deal with these issues. Having people who can take over for the employee is critical. There’s a lot of factors that go into this, such as type of project, amount of workers, etc. but a strong capable team is the best way to deal with this issue.