I always give it till day 25-26! I have had a few real late hatches! Like on day 25!!! I have had 1 set go completely silent until day 22 then that night they all popped out within 8 hours. Dont give up yet! My last set got lost in the mail and a few got crushed. I still put them in the bator and had 2 hatch out of 18! Stupid PO!!! But they are the sweetest lil hens you could ever want. My DW tried to get me to just toss the lot at lock down. I candled when moving them into the hatcher. When only 2 showed development she said " Just toss them all, they are prolly all dead any way!" Guess I showed Her! LOL Good Luck and God Bless!