How do I set an end date to a recurring task?
unfortunately it's not possible right now, but we will consider adding such option in the future. You're welcome to vote for this request in our Votebox: http://todoist.com/Vote/showProposal/214/
For now, you can either delete such task or, before the last event occurs, set it to the single specific date in order to "complete" it.
My vote has now been cast. Thanks David.