How do you know when to sever a long marriage that has been withering for months, or even decades? This is a popular question I get from readers.

The queries used to come mostly from younger wives who were dealing with new babies and new spouses, all at once. Because of the tough transition from honeymoon bliss to real-time marriage, a common juncture for divorce is at the two to three-year mark.

Increasingly though, as life spans are elongated, I get more angst-ridden dispatches from women 50 and beyond on the fence about following Tipper Gore's lead. This is the brave wife who split from former Vice President Al Gore, after 40 years of marriage. Some of the older women say they are jealous of Tipper, that despite the upheaval of separation, this lovely and youthful woman gets a fresh stab at love and life.

From the hundreds of sagas uncovered in researching my relationship books, I am constantly reminded of the eggshell-thin line that separates loving from loathing. I know that staying married can mean plates flying, tears of loneliness, too much wine, and searching for old boyfriends on Facebook at 3 a.m.

Who stays married and who doesn't isn't always a question about commitment or hot love -- it's about endurance.

During interviews for The Secret Lives of Wives, I heard lots of twisted tales of marriages that have endured -- through threesomes, spouses coming out as gay, having no sex to the wife discovering her husband was sleeping with the priest who was counseling the couple.

This wife and husband who found God big-time are still married, as is the 61-year-old wife in a long affair with her chiseled landscaper while her "doughy" surgeon husband lectures around the world. Nothing shocks me anymore about what goes on behind closed doors. My shock comes from how many outwardly cheerful spouses who have been married forever think about divorce if not weekly, but at least once a month.

Yet, most of those wives remain on the married side of the eggshell-thin line. One 56-year-old in that category describes herself as "questioning all the time, but not miserable" in her 25-year marriage. This is not an abused wife. Her husband gives her orgasms and jewelry. Her laments are about something more subtle:

"I am bored. I am tired of him. I want to be wildly in love. I stay because of fear and inertia. I am aware that the unknown may be worse than what I have."

Persons expressing doubts while determined to stay married share these common traits: Their laments aren't because of anything huge. It's the nuances of living with one person for a very long time that cause a simmering malaise. It's the grind of the ordinary that drives people into thinking, "Is this all there is? I want more. I want adventure. I want change."

Women in their 90s are the fastest growing segment of the aging population, which means that many of us wives could hit our 50th wedding anniversaries and beyond. That's a hell of a long time to sustain one love affair, particularly when empty nest hits and it's only you and the spouse with no cushion of kids.

Some marriages clearly need to end, relationships that are poisoned by abuse, abandonment and infidelity. I hear from those straying partners confused about whether to flee the security of an intact family to pursue the "true love" fanned at the office water cooler. Yet, I remind those in explosive, can't-eat-can't-sleep affairs that that there is nothing like new love, and that the new, inevitably, becomes old. I remind them that they aren't living with their lovers, sharing a bathroom and fighting over bills.

Affairs are fantasy love. Commitment and marriage is hard and real.

The happiest wives who go the distance have a sense of purpose and joy outside of the home. Wives who count on a spouse for fulfillment often express anger and emptiness. Those people who manage to stay married aren't dwelling on "Is this all there is?" They know that they must take charge of their own happiness, with work they love and a tight circle of empathetic girlfriends with whom to drink, travel and vent.

During my own 28-year marriage, my husband and I buried our parents and raised four sons and tousled over piles of bills. I could never have carried on without my sister and girl-circle.

Weddings are perfect. Brides are at their thinnest, most beautiful and most hopeful. Staying married for the long haul means accepting imperfection. We know from others who do call it quits that the grass isn't always greener, there are parched patches on both sides of the fence. Dealing with incensed step-children can be worse than any scene from a lackluster long marriage.

You cannot love your marriage all the time. But if you like your marriage more than you dislike your marriage, even if there are periods of 51 to 49 percent, that can be a better deal than starting over with a sexy stranger whose flaws have yet to unfold.

The marriages that rip apart self-esteem and stifle growth clearly need to end. But boredom is not a good enough reason to divorce. A mediocre marriage can seem a lot more interesting when we seek out other arteries of inspiration that contribute to passion of the soul and self-worth, in friendships, hobbies and work.

Send your questions to Iris at iriskrasnow.com, where you can also find her books. You will remain anonymous, so ask away!

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