Week by week I would check in on them for toiletry items and bedding to be replaced. I think small shampoo/ conditoner capsules are a nice touch. Like @Colleen28 mentioned, taking care of the trash is a nice gesture as a host but it come with benefits to you as well. When I have guests that are staying a long time (month long) I like to bring them some cheap wine to thank them for their stay and to welcome them into the property.
1. Small capsules allow you to check in when you replenish their supplies
2. The small shampoo capsules give the guest a better impression that they are the only ones using the rental rather than sharing a large bottle of soap with previous guests.