I don't refrigerate my eggs at all and I have eaten fertilized eggs as old as 2 months after sitting on the bench top in the kitchen. If they are getting old, I test them by placing them in a jug of water. If they stay on the bottom, they are ok, but I normally break them into a separate container just to be sure, before I cook them. If they look ok and smell ok, then they are ok in my book, but I do thoroughly cook these older eggs rather than leave the yolk runny. ....;. If they float then I take them outside and break them in the garden somewhere out of the way, as they may explode and if they do, they stink of..... well .... rotten eggs.
As Michael says, your handling and storage conditions will effect the longevity to some small extent.
As regards fertility, you need to crack a few open and look for the blastoderm.... a small whiteish spot on the yolk. If the spot is small and well defined then it isn't fertile but if it is expanded and looks like it has a halo or bullseye, then it is fertile. There is a thread on the forum with photos which shows you what to look for.... if you search the word blastoderm you should find it. Of course you can't hatch the ones you crack, but it gives you a good indication of whether the other eggs will be fertile
I find that hens and roosters that have been hatch mates(and are perhaps siblings.... which is possible/likely if you got them from a breeder rather than from a large hatchery) are slower to mate than when they grow up in a mixed age flock. I have some welsummers at the moment that are nearly a year old and are only just showing an interest in their pullet hatch mates. Unfortunately the girls are not accepting their advances. It's funny because they have been dropping a wing and dancing for each other (but not actually trying to mate.... just doing the courtship bit) for months and I was coming to the conclusion they were gay, but at last they have noticed the girls!
Like you, I thought that I perhaps just wasn't seeing them mate the girls, but I am retired so I am here a lot of the time. I checked tsome eggs and they were not fertile. I even put some under a broody as I really wanted some welsummer chicks but none were fertile.... thankfully my marans eggs provided some chicks for my broody. Unless your cockerels are very shy, I'm therefore less certain that mating is happening if you are not seeing it.
Is there any reason why you are keeping eggs so long.... it happens to me because I have far too many hens ....no.... that's not correct.... because, of course, we all know you can't have too many hens!!!...... What I meant to say is that I don't have enough friends and family and neighbours to give the eggs away to, when my chucks are all laying well. If you are wanting to incubate some then, 2 weeks old is usually considered the oldest they should be for a healthy hatch.
Regards
Barbara
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