Question about dove eggs

A friend who has a beautiful dove pair who he has been taking eggs from and throwing them away for months just gave me two of their eggs to hatch by one of my dove pair. Im looking to add some different genetics to my flock. The first two eggs he gave me I put into an incubator for a week or more and never saw any vein development by candling them. He just gave me another two eggs but now Im wonder if they will develop. He has let his pair brood young in the past and gave one of the offspring so I know that this pair CAN produce viable eggs.
The question is does constantly taking away the eggs from a pair lower their chance of producing viable eggs? By not letting them brood, hatch and raise their young is their enthusiasm dashed so badly that they stop copulating?
Anyone with experience on this matter?

Note:
The reason my friend doesnt want to let his pair hatch babies is because his aviary is very small(4 X 6 X 8' tall). I built a large aviary (14 X 18 X 15' high) so I can comfortably house my flock.

Also, does anyone know how many days of incubation is required before evidence of growth is seen in a candled dove egg?

Quote: Ask your buddy to let you house them for a couple months. They will breed now until about September if give the chance is my experience.

why don't you let your friends pair raise the young and you get the babies at weaning ? and yes if you continue to throw eggs away sooner or later the hen will have problems most people that foster eggs under other pairs do it two or three times then let the pair raise a round they will let the hen set on eggs for ten days to keep then in cycle and not wear them out

We tried that by giving me an oops baby, a single offspring. Unfortunately the others in the aviary were so mean to her that they chased her away. She somehow escaped and I could not get her to come back in the aviary as she didnt recognize it as her home. Im sure a hawk got her as she was a little albino and stood out among the other birds like a sore thumb not to mention she had no experience living in the wild. We decided the best way would be for me to take eggs and let my dove pair raise them as their own. Unfortunately for me his wife has a thing against polluting the world with doves and so she snatches the eggs and throws them away before he is able to get them. When he found out my first dove, Cyrano, who he gave me flew off and was killed he focused on getting eggs for me. Im just not sure that they will be viable. Regarding letting his doves stay with me, I doubt that is possible. I will of course take them in if he and his wife ever decided to rehome them. I have plenty of room for them in my aviary and maybe in a pair they wont be so easily chased away by the other who have made the aviary their home.