Egg fertilization

I'm sure this has been previously discussed, but I would like to know how long will hens continue to lay fertilized eggs once the rooster has been removed? For reasons discussed in another posting under the nasty rooster category, I will soon be stewing my rooster. I had planned on breeding some within the next several weeks and have begun to set up the incubator etc. I would expect that fertilization occurs weeks before the egg is laid, but am curious how much time I would have to collect fertilized eggs once my rooster is removed. My rooster (a Rhode Island Red) is just a year old, but I believe he has been at all or most of the 21 hens, most of whom show the "hen tramp stamp" on the upper saddle, so I am hedging that most of the eggs have been fertilized. Of the 15 eggs per day about half are of incubator quality. I think one or more of the hens are laying eggs in the woods, although head count places them all in the coop at night.