See, but unlike Eragon these eggs don't wait to hatch until the right "time" or the right "person" comes along.
As long as the eggs are fertile (which doesn't happen all the time) and kept warm, they will hatch.
If they are wild dragons, the mother helps the baby inside hatch.
If they are eggs that are in the care of a potential rider, it is that person's responsibility to help them hatch.
Sapphira never thought that Eragon was her "mommy."
I'm not sure how I'm going to work that out, honestly.