@Kate867 Some hosts who take long term bookings have said it's a good idea to go in once a week to clean. If the guests are messy, dirty types, which you have no way of knowing, it's better to keep it at bay, rather than let a month's worth of dirt build up. I've read some horror stories here on the forums about the state hosts found their place in when they just left the guests completely alone, without going in to clean, for a month.
And make sure, if you are going to leave enough bedding and towels in the unit for their entire stay, that they are clear that that is all that is provided. What might be obvious to you or me isn't to many guests. You want to avoid having them use a towel once, throw it on the floor and take a fresh one off the pile every time they have a shower, then asking you for more, or running the washing machine daily. If you decide to have your cleaner go in once a week, yu might want to provide them with enough for a week and have the cleaner bring in fresh stuff then, if that's practical for you. And if you do have it cleaned once a week, it's fair to charge a cleaning fee.