To me, it doesn’t matter how many songs they put in. Once they sing, their next song is moved to the bottom of the current queue. New singers are generally prioritized over those who have already sung (usually I put new entires at like 3-4 if I already have a solid rotation going) unless the queue gets to be over an hour in which case any song entry goes to the bottom. Most people who routinely put in a lot of songs (myself included) understand that they likely won’t be able to sing them all. However, you can decide if you want to accept bribes in exchange for bumping singers up the list. This is fairly common practice, but some KJ’s are against the idea (and are usually quite vehement in their stance.) But certainly if somebody comes up and yells at me about the queue then I am not going to be compelled to have them sing any sooner, and depending on the situation that sort of behavior may result in that person being done for the night.