Mallard Not Sitting on Eggs

I have 2 Mallard ducks and the female laid about 20 eggs the first time this year and never sat on them and since has laid 2 others next in the yard that predators got. So I cleaned out the solarium and put hay down and she made another nest and has laid more eggs. Three days ago she started sitting on them all day and then today she has been roaming with the male for almost 4 hours now.

How long does the female Mallard usually leave the nest a day to eat once she has started sitting on her eggs? Do you think she will go back to sitting again?

By Reannon S.