Sebastapol Goose Eggs: How Old is To Old to incubate???

[JordanFamily]

This lady wants to sell me some goose eggs and says some are 3 weeks old, but she says she never sales them after 3 weeks of age do to viability going down after that... So is three weeks old to old to incubate??? What is the oldest egg you have incubated successfully before??? Thanks

 

[Meleda3]

I was told no more than 12 - 15 days for turkey eggs. I'm not sure about chicken eggs.