I used to do this, but ran into a few catches. They usually honored it for a day, but beyond that they need to check that you're not trashing the room & that t

I used to do this, but ran into a few catches. They usually honored it for a day, but beyond that they need to check that you're not trashing the room & that they don't have a deceased guest on their hands. At one hotel, cleaning staff explained to me they were getting in trouble for not cleaning my room, and that they had a daily random check around mid-afternoon by their higher-ups. It also prevents them leaving early if they finish all the rooms, because they still have to wait for your room to become available. (Hence the midday "sorry to disturb do you need any towels" enquiry... they want to at least cross your room off their to-do list.) Nowadays I still put up the DND sign, but take it down anytime I'm leaving the room for a while to give them a chance to clean it.