That depends on the hen Dave, my Dad had a hen that flew really well having just laid her 2nd egg, inc. with the national at 500ml. Knowing this I have done the same with mine and it has worked well with one in particular, even waiting on her to lay before heading off to club, pooled and nominated her, and it paid off on a couple of occasions before I stopped her for breeding with. However most of the others preferred to be sitting a few days longer, suppose if you dont try you wont know?! ATB, W.D.