@Stephen1579 When I did long stays (I don't any more) I would add a mid-rental or weekly cleaning fee which allowed housekeeping to go in and change the beds and clean the bathrooms. This had to be scheduled with the guest and paid for prior to arrival, as AirBnB does not have an option anywhere to add mid-rental cleaning fees.
Allowing housekeeping mid-rental meant that I had an eye on how the guest was treating my property. If you cannot do this, providing the guest with an extra set of sheets and towels should be adequate, assuming that the guest knows how to use a washer and dryer and will change the linens (amazingly, some do not).
Communicate with your guest and establish what is going to happen -- they change and wash or you come in periodically to do so.