NO need to panic. Eggs in their hard-boiled state aren't the time bombs we once thought they were.

Hard-boiled eggs should last several weeks in the refrigerator, says USDA home economist Betsy Crosby. And even the ones that stay hidden under the sofa for a few days will be all right. In any case, you'll notice a stale or "off" flavor as they begin to age. The off taste doesn't mean they're contaminated, however, just old. An Easter egg bad enough to make you sick "probably wouldn't get past your nose," according to Crosby. The chances of becoming ill from a hard-boiled egg, even an old one, are remote, she says.

Eggs are notorious borrowers of their neighbors' tastes and smells, so they should be protected during their stay in the refrigerator. Try to use those with cracked shells first, since the shell is a natural protector against borrowed odors and flavors. The ideal way to store hard-boiled eggs is in the shell in an egg carton. If you want to store shelled eggs, wrap them in plastic or place in a plastic bag.

As for what to do with them, here are a few suggestions:

* Salads. Chopped or sliced, hard-boiled eggs go nicely in tuna, chicken or potato salad. Or, try a salad composed of alternating tomato and hard-boiled egg slices. Pour a mustardy vinaigrette over the top. Potatoes, cooked, cooled and sliced, can be used in addition.

Sieve hard-boiled eggs over salad greens or over cold green bean, beet or asparagus salads.

* Creamed eggs. To serve four people, add eight hard-boiled eggs to two cups of bechamel (white sauce). Serve over toasted and buttered english muffins with or without a slice of ham or canadian bacon. Sieve another egg over top, if desired.

* With matzo. Butter matzo and lay sliced, salted eggs on top.

* Stuffed eggs. Slice eggs in half lengthwise. Sieve yolks, add heavy cream or mayonnaise to make yolks the consistency of thick whipped cream, add mustard, salt, pepper and herbs or curry powder to taste. To dress them up, pipe yolks back into whites with a pastry bag fitted with a star tip. Sprinkle with chopped parsley or paprika. Or, if you're really feeling fancy, protect one half of the top of the egg with a piece of paper while you sprinkle on paprika, then protect the paprika'd half while you sprinkle with chopped parsley. Try adding chopped ham or crumbled bacon to yolks.

* In meat loaf. Lay eggs end to end in the center of meat loaf mixture, so that when it's baked and sliced every serving has a slice of egg in the center.

* With caviar. Even if the dye leaked and the whites of your eggs are shocking pink, who could care? Surround a mound of caviar with chopped egg and chopped onion. Serve with toast. SPINACH AND EGG GRATIN (3 to 4 servings) For the white sauce: 2 tablespoons butter 2 1/2 tablespoons flour 2 cups milk Salt, pepper and grated nutmeg to taste For the gratin: 1 tablespoon butter 2 shallots, minced (optional) 10-ounce package frozen spinach, cooked and drained 6 hard-boiled eggs, halved lengthwise, yolks removed 2 tablespoons grated swiss cheese

Make white sauce: melt 2 tablespoons butter in saucepan. Add flour, stirring and cooking over medium heat until flour is well blended and mixture bubbles. Add milk a little at a time, stirring constantly. Season with salt, pepper and freshly grated nutmeg to taste.

Melt 1 tablespoon butter in heavy skillet or saucepan. Gently saute' minced shallots until they are transparent. Don't let them brown. Add drained spinach and saute' to get rid of extra moisture. Sieve yolks from 3 eggs into spinach and mix.

In a gratin or other shallow baking dish large enough to hold the 6 halved eggs, pour 1/2 cup of white sauce. Stuff egg whites with spinach mixture and lay them in the baking dish. Sieve the other 3 yolks over top, then pour over the remaining white sauce. Sprinkle with grated cheese and run under broiler to brown. Or, if ingredients are cool, bake at 425 degrees until brown. HARD-BOILED EGGS WITH TUNA SAUCE (4 servings) 3 1/2-ounce can tuna with oil 1 teaspoon dijon mustard 2 scallions, cut in 1-inch pieces 2 tablespoons lemon juice or good vinegar 1/3 cup olive oil Salt and pepper to taste 8 hard-boiled eggs Lettuce

Put tuna with its oil, mustard, scallion and lemon juice in food processor container with the steel blade. Process until smooth. With motor running, add olive oil in a thin stream and process until sauce is thick and smooth. Add salt and pepper to taste. Halve or slice hard-boiled eggs and arrange on a bed of lettuce. Serve with sauce on top. Black olives and slices of green and red bell peppers make a nice garnish.