I added mine when mine were about 5 months old. Nobody seemed ready to lay but I wanted them to have time to get used to them and "test" them out. I put golf balls in from the very beginning. I have mine on a shelf, so there is about a foot of space in front of the actual boxes for them to jump up on and walk around. They were curious and would jump on the shelf and then step in the boxes (I use square plastic storage containers that look like dish pans with holes in the sides. I fill them with straw) and pick at the straw a little. Mine just started laying at the beginning of November (23 weeks old), and all have managed to lay in the boxes. I have found two on the ground, but they were obviously from new layers (they were very small), and I just think they didn't make it into the nest boxes in time and they plopped out onto the floor. I just collected 6 this afternoon from my 9 pullets - yesterday it was 5 so someone new is laying (29 weeks old)! Good luck!