It depends on the hen! Some just don't go broody. It does not matter how many eggs they lay. I have some that will just have the egg they lay that day and they go broody. (I collect eggs daily)
Typically i believe they will lay 6 to 8 in a clutch before they stop laying. My two broodies are like patyrdz says. They will sit on an egg someone else lays and not move or lay more. Do a search to find how to make hens go broody. It is an interesting and debated topic.