I agree with the virgin part, that is a very good point and crucial if you want to guarantee your hets.
I'm not so sure on retaining when they dropped eggs the previous year though, if that has happened it has to be extremely rare, but lets just say I'm skeptical.
I bet you'll find many breeders breeding recessive traits to females that gave them eggs the previous year.
I have bred virgins to make all of my morph hets except this year I'm doing bumblebee again to clown.
She went last year but was bred to our clown and delivered a sweet clutch.