Because I have three egg cartons in my 'fridge

Here's a handy way to tell if your eggs are fresh.

Place an egg at the bottom of a glass full of water and watch what happens:

If the egg lies at the bottom on its side, it's fresh.
If the egg sinks, but with one end up, it's getting old but is still edible.
If the egg floats at all, you should buy some fresh ones.

This test is effective because eggshells are porous — over time they dry out, letting air in and moisture out.