If a mama duck gets scared and leaves her nest and it is fifty degrees outside how long will it take for the eggs to die?

One view: It actually depends on the age of the embryo in the egg. An older embryo will warm the egg and the egg will stay warm longer. If you feel of the eggs and they are losing warmth, she has probably abandoned her nest. She knows the age of the chick and how long the eggs can be without her.