A feed should say when it stops being true. A calendar that runs until 2099 says "forever", which means a trip planner will keep showing this timetable long after the routes change, and nobody can tell an outdated feed from a current one.
The law
The last service date is more than five years from today.
How to get pardoned
End the calendar at the end of the timetable period, and publish a new feed when the next one is ready.