over 21 days can they hatch?

[joshyoua_rine]

My hen give up at day 20 due to mites and i caught it that night put it under a eat lamp and today was day 23 i was giving up and cracked one and a chick was inside and it had a heart beat. i had 18 eggs to many i know now but how long can it take? the chick was fully developed even had feathers but yoke was still attached. temp is 100 degrees

 

[abbylane35]

I have had eggs hatch as late as day 25...so there is still hope yet! I hope that you have some success with this! It is always frustrating when a broody gives up (for whatever reason).