She will be 80 on July 4, but Abigail Van Buren is no staid octogenarian. "I'm shockproof," says the advice columnist the world knows as Dear Abby. Mention any topic and she's ready with an opinion. Viagra? "It's wonderful," she says. "Men who can't perform feel less than manly, and this takes them right off the spot." Twelve-year-olds having sex? She strongly disapproves but adds, "Kids grow up awfully fast these days. You should try to have a good relationship with your kids, no matter what they do."

After 42 years in the advice business, Van Buren—like her twin sister, columnist Ann Landers—has heard it all. And she says it has changed less than you might think. "For the most part people's problems are not new," says Van Buren. "They're having trouble with their mother-in-law, they broke up with their boyfriend...." Yet she hasn't tired of her role, and neither has her public: Van Buren's daily column, currently syndicated in 1,200 newspapers, provides pithy counsel on everything from deadbeat dads to living wills for some 90 million readers worldwide. "I write short, and I use humor," Van Buren says. "It seems to grab people."

And has from the day in 1955 when she persuaded the San Francisco Chronicle's editor that she could do better than the paper's advice columnist. "She wrote too long," says the 5-foot-tall Van Buren, the younger daughter (by 17 minutes) of Abraham Friedman, a Sioux City, Iowa, movie-theater owner, and his wife, Pauline. Nee Pauline Esther "Popo" Friedman (her sister "Eppie" was Esther Pauline), she took a pen name because it was common practice, and Van Buren, she decided, "sounded solid." Over the years, she kept writing short—but not always sweet. Her support for abortion rights drew reader flak. "It didn't bother me," she says. "I went right ahead."

She still does. In her office in the grand Beverly Hills French Regency home she shares with her husband, retired businessman Morton Phillips, also 80, Van Buren works at least eight hours a day, assisted by a staff of six who sort the 1,000-5,000 missives she gets weekly. "When the sun is up, she's up," says her daughter and editor Jeanne Phillips, 56. (Son Edward Phillips, 53, runs a wine distributorship in Minneapolis.) Van Buren writes on an IBM Selectric typewriter, interrupted now and then by a chatty fax from sister Eppie in Chicago, whose own column is also going strong. The twins' decade-long feud, brought on by professional rivalry, ended 30 years ago. "We're friends. There's more than enough out there for both of us," says Van Buren, who discussed her long career as a know-it-all with PEOPLE correspondent Danelle Morton.

When you approached the editor of the Chronicle four decades ago, what made you think you could give other people advice?

I was cocky. My contemporaries would come to me for advice. I got that from my mother, the ability to listen and to help other people with their problems. I also got Daddy's sense of humor.

Is there a typical letter writer?

I get mail from men, women, teenagers, everybody. Women usually pour their hearts out. Letters from men are shorter—they want a quick solution to a marriage situation or a problem controlling the kids. Teenagers usually say, "My parents don't understand me at all."

You say most of the problems people want your advice on aren't new. Has your mail changed at all since 1955?

The world has certainly changed. I think some of today's problems stem from the economic necessity of having two working parents and the fact that the parents are not around to discuss the typical problems of growing up. So even though the problems aren't new, circumstances are different, and everyone is under a great deal more pressure.

Do you think families would be better off if mothers didn't work?

No. I think it's good to have a woman work if she wants to and doesn't leave her children unattended—if she has a reliable person to care for them. Kids still need someone to watch them until they are mature enough to make responsible decisions. And parents need to let their kids know that, even though time together as a family may be short, they can talk to their mom and dad about anything.

Has the advice you give changed?

When I first started the column, I was reluctant to encourage couples to divorce. I always thought that marriage should be forever. I found out through my readers that sometimes the best thing they can do is part ways. If the man or woman is a constant cheater, the situation can be intolerable. Especially if they have children—when kids see parents fighting, or even just sniping at each other, I think it is terribly damaging.

What was the strangest letter you ever received?

I got a letter once from a man who was in love with his pony. I mean really in love—we got a picture of the pony, so help me. If I printed it people would think I was making it up. There's no reason to make up anything. There's nothing weirder than what I get in the mail.

Do you get much hate mail?

Not serious threats. But every time I say a kind word about gays I hear from people, and some are damn mad. People throw Leviticus, Deuteronomy and other parts of the Bible at me. But it doesn't bother me. I've always been compassionate toward gay people. People are shocked by some of the things I discuss in my column, but that's their ignorance. You can't help that.

How do you handle letters from people who sound suicidal?

Often, I'll call them. I say, "This is Abby. How are you feeling? You sounded awfully low." And they say, "You're calling me?" After they start talking, you can suggest they get professional help. Once I called a woman's doctor for her. I told the nurse, "This is Dear Abby. I heard from a patient of yours, and she sounds desperate. She said she can't get an appointment for two weeks—please see her as soon as possible." The doctor saw her that day.

So you think you have a real impact on people's lives?

I know I do.

Which of your columns prompted the largest reader response?

One of the largest was in 1986, when I asked married readers to write me about whether or not they had been unfaithful. I got 210,000 letters, and I was astonished—and reassured—to learn that the marriage vow is still honored by 85 percent of the females and 74 percent of the males who responded.

So many of your letters seem to be about sex. Is it really so important?

It's very important to some people and not important at all to others. Some women just tolerate it. They could do a little acting now and then. It couldn't hurt. A little heavy breathing. Move a little bit.

Do you consult with anyone?

Sometimes. I can run things by Dr. Judd Marmor, a top-notch psychiatrist and a lifelong friend. I get medical advice from doctors at the Mayo Clinic. And on general legal issues I consult Los Angeles attorney Arthur Groman. I also have a husband who is very intelligent. He gives me the male point of view, and he is unerring.

You and he have been married for 59 years. What's the secret?

Don't be too judgmental. Keep your cool if something really bothers you. Be totally honest at all times. And don't criticize anyone in his or her family. There are lots of fights over that—your mother, your father, your sister.

Speaking of sisters, was it difficult growing up a twin?

No. "We got all the attention. We dressed alike until the day we got married in a double ceremony.

Some people with a background like that would end up on The Jerry Springer Show—"Forced to Look Like My Sister!"

Isn't that show wild? I think it's rehearsed. But, no, we were the cute little Friedman twins.

Do you ever think about retiring?

No. I try not to think about it. I don't know what I'd do with my time if I wasn't working. My job isn't a burden to me; it really is a pleasure. I can't wait to get to work in the morning.

As you approach your 80th birthday, any tips on how to grow old gracefully?

I wish I knew. I suppose just acceptance. You don't have to grow old; you're just getting older.