Store bought eggs are usually around 2 months old. They should really be collected at least twice a day, if only to prevent them from getting broken and the chickens eating them. If the chickens start eating the eggs, it is almost impossible to break the habit.
Eggs should not need cleaning. Teach the chickens to sleep on the roosts and do not let them sleep in the nests, and they won't get poop on the eggs. If you just have to wash them, as some feel they must, be sure the water is warmer than the egg, so that bacteria will tend to move out of the egg rather than into it. But when you wash them, you wash off a natural coating that the chicken leaves on them, which helps preserve them.
