You need to be strict about it. It's amazing how many "emergencies" aren't emergencies. If I have plans I have plans. If there are loads of "emergencies" then

You need to be strict about it. It's amazing how many "emergencies" aren't emergencies. If I have plans I have plans. If there are loads of "emergencies" then that is the result of poor planning and management. Lots of managers I have worked with back off when I decline. Having said that, not everyone is in a position to be strict about it. It needs to be put into law or hashed out during the hiring process.