I think it is best to wait until the chickens are about eight months, so that the chickens can properly develop their egg laying skills and you won't risk an egg missing a yolk, missing the shell, being funny shaped, being extra small, etc. But if you want to give it a shot, to see if it will work, then I don't suppose there is much harm in trying.
I agree with the other posts. Usually when a pullet starts laying the eggs are small and the chicks that hatch out are runts. Many times the runts will make it for a few weeks then may die. The chicks have a better chance if the eggs are a little bigger then the chick that hatches out is larger. I was given some eggs from some new layers and several died. I do have a survivor so far that hatched out of an 38 gram egg. It was hatched out 2 months ago and is still the size of a two week old chick but it eats, drinks and poops good...
I've hatched out a lot of pullet eggs with no problem.
the batch of my eggs that I have in the bator now are all pullet eggs.. out of 24 only 2 weren't fertile. I don't expect any problems with the other 22 hatching or the chicks thriving.
the last batch of shipped eggs that I set that were light brahmas.. I added in a few pullet eggs.. out of all of the eggs that hatched the pullet eggs had 100% hatch rate, the shipped eggs were less.. the pullet egg chicks were just as big and healthy as the eggs from adult hens.
to this day they are all alive and well and growing according to schedule
I'd say it depends on the egg. If it's a good size, normal shape and the shell looks good go for it. If it's a teeny tiny egg with a wonky shell, I wouldn't try it. That said I bought a dozen hatching eggs and got one 'pullet torpedo' a very odd long skinny egg, I wouldn't have set it if my girls had laid it but since I'd paid good money for the eggs I set it and hoped for the best. It developed and though I had to help it a little hatching it turned out fine.
Let us know how it turns out if you set it and good luck if you do.
I ended up eating it and my JG laid me another today a little bigger, but perfect shape and not poreous. so I plopped it in the bator..
I had an eventful weekend, one hen laid a double yoker, one hen laid two eggs in one day, and my Jg laying like a champ. SO happy.:]
Now for my wyandottes to start laying.....
Many of us "chicken folks" have done things we SHOULDN'T have done. Sometimes it works out perfectly and sometimes, not so much. Consider your possible pros and cons, then make the best decision for you. If you accept the odds of a good vs. a bad hatch experience, then I wish you the best of luck! Healthy hatching vibes coming your way.