@Bethany27 I know there are hosts who will tell you that it's absolutely unacceptable not to wash all the bedding between every guest, some even feel they have to wash the mattress pad every time.
I'm not one of those hosts. It is only chilly enough for a duvet a few months a year where I live, and I don't wash the cover in between each guest. I use top sheets and fold them well back over the top of the duvet. I don't take one nighters or back-to back bookings, so I can hang the duvet out in the sun and the breeze while I'm cleaning the guest space. I only host solo guests, so it's not like anyone's been having a sex romp on the bedding. I have a spare cover, so if a change is needed, I don't have to right away do a wash. If I have a guest who leaves a bit of odor in the room, or the guest didn't strike me as particularly clean, or the duvet doesn't smell clean, I'll definitely change or wash the cover. If I have a single female guest who doesn't smear herself with makeup and self-tanner and I can hear the shower running at least once day, I don't necessarily feel the need to change the cover. I do wash the covers on a regular basis, just not necessarily between every guest.
Yes, many hosts struggle with putting the duvet back in the cover- it's a matter of practice and there are a few methods that people use. I don't find it very difficult myself- I lay the cover out, hold the top 2 corners of the duvet and reach my hands up inside the cover to put those corners in place. Then grab those corners from the outside, holding onto the duvet corners themselves and the cover corners in each fist, then just give it a good back and forth shake. Bottom corners may then need a quick tuck in place. Not that hard, but I know some people get fussed about finicky things like that.