I would love it if Airbnb would offer the ability to have different cancellation policies based on a guest's length of stay. For short stays we like to go with the moderate cancellation setting - give a full refund if cancelled more than 5 days out, however for longer stays of a week or more we want to have a non refundable deposit and require a longer cancellation notice time.
We have this set up with guests who reserve directly with us, as longer term stays are a lot harder to re-book, and having a non refundable deposit also ensures that a guest who books a long stay is not just blocking off nights when they are not sure about actually staying.
Thanks,
Chris