I have been putting mine together if they are around a week apart, when the newbies are a couple of days old. It has worked out fine for me.
I just posted a craigslist add to hopefully sell my mixed breed babies from the EHAL, my DH was "egging" me on to SET ALL THE EGGS! If you can, and don't have any yourselves to sell, will you please pass it around and on. I will have lots (50+) that I need to get out of here! There are many more purebreds included in this hatch that I will sort through and sell at a late date.
http://spokane.craigslist.org/grd/5501648021.html
Thank you!!