yes some ducks don't like empty nest. so I usually leave one in it for moscovies. indian runners are okay to take them all.
I will try golf balls for next time moscovies start lay eggs. I thought golf balls are too small.
In my option for hatching, I pick and store the eggs upside down (air pocket at below). In this way keep the eggs away from dirty.
When the time one or two went to broody. I put them back to the nest. usually not more than 12 eggs in one nest. Some people said not more than 9 days old eggs. in my case 11-12 days eggs usually still hatched. that is for my moscovies. cause I still un-success to hatch moscovies eggs with incubator. But the hen can done very well. a week ago one was hatch 11 out of 11 eggs and the other 10 out of 11 eggs. total 21 duckling.
When before I not collect them, some of the earlier eggs usually become dirty before broody. most of them will kicked out from the nest before the final day. because they are developed bad smell. the rate are around 50%