I’ve never seen luggage traveling in covers. I’m trying to visualize the carousel at baggage claim and there are no covers in my memory. Given that the airline industry seems to go from crises to crises in recent years, we never check bags unless we need to check a bag on the return trip due to purchases (rarely done.)
We can do 12 days (easily) with our carry on and the largest possible personal item that will fit under the seat. If we go 14, we spend a couple of hours doing laundry mid trip.