I had a vague idea that Marketo had a landing page expiry function but can't find anything about it. Must be only in my dreams 🙂
An old thread here but has a valid suggestion of using javascript to do a redirect after a certain date. May still be your best option:
https://community.marketo.com/MarketoDiscussionDetail?id=90650000000PQCSAA4
Or you could always manually set up a redirect at the appointed time but that involves a reminder to yourself and manual work (boo).