Depends if you are buying straight from a farmer or from the market. If you buy from a farmer then usually the "bloom" is on the egg. The "bloom" is a microscopic thin membrane that protects the egg from the outside environment. If you have these kind of eggs, they can sit on your counter (yes not refrigerated) for up to 2 weeks. You refrigerate these eggs up to a month.
If you buy store bought, then the bloom is washed off and normally the egg is bleached to kill any potential bacteria because the shell is porous. These eggs don't last as long because they went through a long process just to arrive at the market and into your refrigerator. I wouldn't keep them much longer than a week to be honest.
5 dozen * 12 eggs = 60 eggs
60 eggs / 4 eggs per day = 15 days
15 != 18
I get 3 dozen eggs, go through 3.5 a day, and finish them yesterday.
For farm fresh eggs, they last at least a month to 6 weeks in the fridge. Regular store bought eggs might last 2 weeks in the fridge. But you can always test them for freshness with the float test. Float them in a deep bowl of water. If they sink that are fresh, Stand on end means they are on their last days of edibility, and if they float toss them out.
I regularly keep store-bought eggs for 3-4 weeks in the fridge. I've never had an egg go bad actually.
I bought 7.5 dozen on the 5th, and we're down to the last dozen now; still okay. PLEASE NOTE though, that I have a half-dozen in the freezer, seasoned and ready to make grain-free pizza crust!
If you're wondering how long they keep in the fridge, it's definitely at least several weeks because that's how long I usually take to get to a particular dozen and use them up.
I can't always find organic, so if I do I "bump" them to the top of the list but I've never had a problem with eggs getting too old to work in recipes or taste good.