Dunno if the feature is already exist, but I think it's a good idea that timetastic will remind user through email if there's plenty vacation days that the user haven't use when it comes to end of year. Just a reminder..
Fab product. I can now book my work holidays online with Timetastic. I just enter the dates I want and get a confirmation email as soon as my boss approves it. No waiting about for days while the holiday form gets lost!