Hi, it really depends on the host, everyone does it differenty. But before entering a space the guest is renting it is important to let the guest know and approve.
I provide linen and towels for their arrival, changes are not included. I charge for the change (but I don't do the changing, I exchange them with the guests and they are responsible to keeping the personal space cleaned. I heard a host say that for long term guests he leaves the sheets o the bed and an extra set in the closet, the guest is responsible for cleaning them if they need more change. I don't do that because I would have to oncrease the cleaning fee a bit to cover the extra sheets laundry bill and I don't think that would be fair for the short term guests.
I also heard a host say she changes them every 3 days like hotels. I think that is too much, we are not hotels. If you want to change them I think once a week is good, you don't need to do more often than that. If they request, you can always charge extra.