This is relatively easy to determine oneself, for when you are booking a hotel that might have such a lounge, just go to the room rate that offers a concierge floor room and read the rate rules -- if the lounge is closed, it will say so, and also tell you the hours it is open.

If on the other hand, it is open, it will not mention any closure and it will, I believe, state the hours the lounge is open.