How long will egg yolks keep?
Egg yolks, optionally covered with water, and in a well sealed container should hold for about 2-3 days in refrigerator.

You may also freeze them, but they require treatment with sugar or salt to prevent the proteins from turning them rubbery, at ratio of about (per the Egg Board):


1/8 teaspoon salt  OR
1 1/2 teaspoons sugar or corn syrup 


per 1/4 cup of egg yolks (about 4 yolks).

Of course, you then have to adjust whatever recipe you use them upon thawing to account for the sugar or salt already mixed into the yolks.

See also:  Still Tasty