Silkies will sit until something is born, Some have even died trying, Literally DIED while sitting because they refuse to get up or get off until a little one pops out, They are EXTREMELY dedicated but is also there downfall. I had one sit for 2 MONTHS, I had to bring her water and food, finally I hatched out a kid for her. She was a very pleased mommy then. LOL She didn't even have any eggs under her once the first batch failed. LOL but she kept sitting..... My Maran, she's just an over protected big mongoose, her problem is she will sit on Multiple eggs at one time, I mean Multiple, I counted 38 eggs under her one time. Most of them broke because she's soooo Heavy her weight smash them but she was determined to have a kid. LOL Cochins, well they are slowly learning, they are a little more impatient but can be very protective, they don't like to sit for a long time, once there clock says OK times up, that's it it's Time up.. LOL.. They can be very easily distracted too.