For shorter stays, we do not change the linen - but generally for longer stays, we change the linen and towels every 4 days.
We have several apartments in a single block. We have fixed keyboxes outside, with each numbered and having a different code. We send the details to the guest prior to arrival so they can check...
I run 4 apartments but used to run larger hotels so the laundry and ironing issues had to be resolved! The key to easier & faster ironing is all about how you fold your linen! If folded correct...