Presumably when Apple adds a film to iTunes for customers to buy they know how long they'll be keeping it on their servers for people to access it. It'll be part of the license. Unless Apple can guarantee that the film will be available after that time (eg Apple negotiated a non-revokable extension that they'll legally bound to take) then it doesn't seem entirely unreasonable that they should have to communicate the time limit to the user. Eg add some fine print that says "This film will be available in your Apple account until 2031, and may be available after that date" or something.