To find out what stairs you can currently challenge someone in, first go to the Main Stairs Page, then click on "Show your stairs only" link. The ones in BOLD are ones you can make a challenge in. .
MadMonkey: Fencer was already going to impliment taking away of empty stairs, I believe he said monthly, but your suggestion punishes the person who makes it to the top and then wants to wait for someone to catch up, he should not have to play until someone proves worthy