I have a down pillow that must be 20 years old. It’s mine and so I’m not grossed out by it. The down/feathers are so old and compacted that it’s lost a lot of fluff but I still love it.
The pillows for the airbnb are chopped foam. That foam can be moved around so compared to a solid piece of foam or polyfill it’s not going to break down as fast. Also they were way overfilled so I took the extra foam out and am storing it. As long as the covers don’t rip, tear or get a permanent stain I could see using them for far longer than 3 years. OTOH if someone just bought a polyfill pillow, put a pillowcase on it and left it for 3 years that would be gross.
I was in a Hyatt within the last two years that had a pillow with a twisted and yellow corner on it that was visible. The Hyatt has no pillow protector on the pillow, just the pillowcase. That corner looked to me like someone had been sucking on it every night for a week. It was gross looking.