One of my closest friends is a millionaire - a brilliant chemist whose pharmaceutical products have benefited many. He calls me at midnight or 1 a.m. or whenever he's ready to zonk out for the night, and raises hell with me for still being at the office.

"I think you must be mad," he says. "Why don't you turn out the light and go home? Do you think Mrs. Graham would fire you if you'd missone dealine?"

What my friend doesn't understand is that he's as much hooked as I am. He doesn't need to earn more money, but he's driving himself to bring out a new antisptic because he has a compulsion to be of service to mankind. Thanks to the generosity of Eugene Meyer and Philip Graham and their profit-sharing fund, I, too, have no further need to earn a living. BUt I'm a sucker for letters from readers. They keep me young, which is more than I can say for the medicines I've been taking.

There is always something to be learned from letters from the readers, even when they disagree with each other. Let me give you some samples of letters that have arrived recently:

M.K. wrote: "I didn't appreciate your cute remarks about postage stamps with religious motif, or stamps appropriate to a religious holiday. I am an agnostic, and the Constitution says I have a right to be an agnostic and not have government-sponsored religion jammed down my throat. Your willingness to accept so-called art masterworks as 'appropriate' to this season disgusts me. Don't you believe in maintaining a wall between church and state?"

R. L. Doty wrote: "Of course you know that the stamp with Washington kneeling in the snow at Valley Forge is a complete phony. A woman George in Alexandria wrote that he prayed standing or sitting with head bowed but that he never knelt. Didn't believe in it."

Mrs. E. A. wrtoe: "Shame, shame, shame. When I glanced at your topic this morning, I thought, 'Bill Gold is really going to get in there and agree that this year's CHRISTmas stamps are the worst we ever put out.

"Alas, another Madlyn O'Hair in our midst. Most stamp buyers agree that Christmas is, after all, a religious observation, and although you coyly refer to previous issues as 'art,' the art depicted is what Christmas is all about.

"I have enjoyed your column over the years, but after this morning's callow and short-sighted observation, what can I say except Bill, I am truly disappointed in you. From now on, the Bill Gold column will no longer be the first thing I read in the morning. Sorry, but where does the word CHRISTmas come from? My good wishes for your good health and re-evaluating the Christmas stamp situation. Happy Hanukah?"

Molly T. Guertler also shook me up a little with this note inside a Christmas card: "My nephew died on Nov. 21 after open heart surgery. Bill, he was home doing fine and the doctors said the new valve was working A-OK.He died in his sleep. The autopsy showed that the valve was working fine but something was wrong with his heart-beat.We are sad. You take care and don't work too hard."

Yes, Molly. A heart surgeon may be agenius, but he's not God.

A military man of flag rank wrote: "Now that you have announced that you can't respond to the friendly letters you receive, I feel free to write what I was afraid to write before: I'm so glad to see you back in the paper."

Helen C. Jackson, bless her heart, put it this way& "Late but sincere! May I add amen to every letter you received while you were ill, saying how we missed your column - how happy we are that health has been restored and that you are back at your desk writing sensible, truthful news, working hard on your yearly project and spreading brotherly love.

"I'm 91 years old, read and enjoy your column every day. May God bless you, keep you well, and may you have a wonderful Christmas with your family."

Gretchen Hood, a mere girl by comparison to Helen Jackson, writes: "Yes, I can top the record of the gentleman who has been reading The Washington Post for 75 years. My father started me readint The Post 85 years ago. May your health be restored to what it was 50 years ago."

Small wonder that my wife says, "I don't have to worry about the sexy blondes you meet every day. The ones who think you're so wonderful are the ones on Social Security. They don't know how stubborn you are."

You don't understand, dear girl. City editors are stubborn. Reporters are resolute.