Anyone who reads the sports pages knows by now that the Washington Redskins famous Over-The-Hill-Gang is gone. But chances are there is another over-the-hill-gang still in uniform on your bar or in your liquor closet.

Check out your first-string vermouth and such important special team players as sherry, port, madeira and even your seemingly indestructible cognac. How many seasons have they been open? Have you sampled any of them recently?

Even though they have been stabilized and enriched by the addition of brandy or another spirit, these so-called aperitif and dessert wines are subject to the same illnesses as table wines. Brandi:s are, too.

One evening several years ago, the famed English wine merchant Harry Waugh was visiting Washington. Prior to dinner he has offered a kir, that Burgundian blend of white wine and cassis (black currant liqueur). After a sip, Waugh wrinkled his nose and, on inquiry, said he felt something was wrong with the drink. A sniff and a taste of the white wine in a separate glass were sufficient to convict it of nothing more serious than lack of breeding. The cassis, however, had a dull, brownish color and smelled "off." It had first been opened, we learned, six months before and had languished behind the bar since then.

Air, heat and bright light all are wine's enemies. In this case, the cassis had been exposed to air inside the bottle and to higher than healthy temperatures. It had oxidized.

Such an illness is terminal. It may be discovered when the wine still is drinkable, or at least mildly infected and still suitable for cooking. But it won't go away. In table wine, if excess heat is a factor, a white or rose wine will become visibly darker in color and take on some of the smell and taste of madeira. Such wine is said to be maderised . Martini drinkers on visits to the homes of non-martini drinkers have probably encountered vermouth in this condition. The first warning is a dust covered vermouth bottle that turns out to be about two-thirds empty. The second warning, if you don't see the bottle, is an exaggerated smell of herbs and a slightly stinky sweetness in the taste.

Some would say it's a just reward for those who drink martinis, but the punishment is even worse for those who take their vermouth on the rocks.

So much for the disease. What's the cure?

First, you shourd understsnd that you are not doing yourself or your potential guests a favor by having a huge display of opened aperitif or dessert wines and spirits. Some of these specialities, vermouth and cassis for example, are sold in half-bottles. Whatever small amount you lose in money, you will more than make up by drinking them in good condition.

If you have decanters and like to display brandy or wines in them, don't transfer the entire bottle. Fill and cork a clean, used half-bottle with the freshly opened spirit and keep it in reserve.

Don't hide your open bottles away in the back of a liquor shelf or closet. Keep them out as a reminder to yourself that they should be drunk and to stimulate the curiosity of guests.

Take a hint from restaurants and feature specials. People are open to suggestion. Encourage guests to taste your new fino sherry. That way several people will drink it when it's fresh. Store it in the refrigerator and be prepared to drink it yourself over the course of the next few days so it doesn't linger and deteriorate. If you want to unveil a port, give the impression that everyone should try it. (Of course, politeness will cause you to stop short of pouring it down an unwilling throat.)