Duck Egg fertility

[Ravynscroft]

Are duck eggs similar to chickens in that they should be set within 7 days or so of being laid?

10 days is optimal viability for chicken or duck eggs, but eggs stored properly can stay viable up to 3 weeks old... just % of viability starts to decrease after 10 days...

 

[Abraeri]

I know this is an old thread - but the same thing is happening to me. I see the drakes and ducks doing their "business" all the time but am unable to see fertilization in the eggs. The flock is 2.5 years old, which I wouldn't think was very old. There are also 4 hatched ducklings who are only turning 1 year old this March.