I forgot to mention in my earlier post, if you know when you are going to be in Vail and you want to ski with that instructor, you can call and book a private lesson requesting that instructor at any time once the ski season begins.
As an instructor at another Vail owned property I can tell you the instructors get paid more for lessons when the client requests the instructor by name. The more private requests an instructor gets the more it helps them in the priority system to get more work, too.
Some clients will book private lessons with their favorite instructor months before the date of the lesson(s). Many instructors will give their clients their personal phone numbers and have the clients call them so they can make sure to be working the day the client wants to ski with them.