@Bethany27
Lots of different opinions here...
The standard is to use a lightweight duvet with a cover in summer and possibly a heavier duvet in winter with a cover. Most Hosts have 2-3 sets of duvet covers so they can swap out the used one with a clean one quickly between guests and launder the used one on site or off-site. Having extra duvet covers also enables you to quickly remove a stained one and replace with a clean one without delay.
Please....for heavens sake - wash the duvet covers between every guest. Same goes for bathroom rugs. You should use low pile, easy to wash/dry bathroom rugs or hotel like bath rugs (they look like a towel).
Large properties sometimes have an extra washer/dryer in a garage or storage area to handle all the linens. One Host I work with has a property that has 16 beds...thats a lot of washing and drying! She has two dryers...one for guests and one in the locked garage and the cleaners use both when drying linens.