@Ana1289 In the case of a 6 week guest, I'd tell him/her that you'll be coming in once a week to change out bedding and towels and give the place a cleaning. It also provides you with an opportunity to see whether they are keeping the place reasonably clean, or whether there is rotting food in the corner, etc. Arrange with the guest what time would be convenient for them.
Most of my guests come for a week-2 weeks. For the one week guests I don't change out anything, nor clean the room, unless they request that (none of them have). For the 2 week guests I offer them clean stuff after a week and ask if they would like me to change it out or if they'd prefer to do it themselves. I've been lucky to have all quite clean and tidy guests (and I leave a broom and dustpan behind the bathroom door and show them where there are cleaning supplies under the bathroom sink if they need them), so all have said it isn't necessary to for me to clean.
If I have a 10 day guest, I'll offer clean sheets and towels at the halfway mark, 5 days, but so far all have said they were still fine with what they had, except for maybe a clean towel and washcloth.