I think it is very reasonable to expect that the T takes care of the schedule and announces any changes as soon as possible. I myself probably wouldn't take these things lightly either and would be very annoyed. Fortunately, my T announces his vacations and free days due to public holidays a year in advance and any other changes in schedule could happen only due to emergency, which hasn't happened during the four years I've seen him. So, to my mind you are not too rigid but just expecting reasonable planning ahead and stability.