Nabiki
Quail Geek
The general rule of thumb is up to a week is optimum. After that, there isn't a set in stone cutoff, but the viability of the eggs begin to drop after a week. After two weeks, you may still get some to hatch, but not many. After two weeks you will be very lucky if any develop.Specifically quail, but really. Any eggs In general. May be a useful resource for others.