The (Occasional , thankfully) practice of putting ALL the floor singers on and then cutting back on the time the guest gets to perform should CERTAINLY be stamped out !
As should letting floor singers Go On And On And On , so reducing the available space for any one who CAN do a good floor spot .
When I was running the evenings at Uxbridge , the times were set in
Re-inforced Concrete - Floor spots no more than Ten minutes , and the time the guest started each set laid down too . IF a guest wanted to do a longer than 35 minute set , two floor spots were dropped in each half !
And it Worked !