WE ALMOST expected that Bill and Hillary would have called it quits by now.

We also understood when Sandra Bullock dumped bad-boy hubby Jesse James, and when Elizabeth Edwards finally gave up on her baby-daddy husband, we cheered. And we respected South Carolina Gov. Mark Sanford's wife, Jenny, for not acting like a typical political wife after her cheating husband proclaimed he'd found his soulmate and it wasn't her. But for former Vice President Al Gore and his wife, Tipper, to separate, that was unnerving.

I, personally, was saddened because the Gores look like the perfect all-American couple. They were the anti-Clintons -you never heard even whispers of scandal. So, for them to announce separation after 40 years, it's hard not to wonder what went wrong.

While most folks respect the Gores' privacy, some of us really want to know, not just out of voyeurism but because you wonder how a family unravels like that. And you also can't help but think that if the Gores can't make it, then what about the rest of us?

With four grown kids and grandkids and enough mansions to never have to share space if they didn't want to, you'd assume that the Gores would be together at least until they died of natural causes, or global warming had turned the planet into a sauna. The high-school sweethearts had already weathered more than a lifetime of challenges, including not one but two terms with the Clintons, hanging chads in Florida, that cringe-inducing kiss at the Democratic National Convention, the near death of a son and Tipper's struggles with depression.

After all that, you'd think they were home free. Divorce-proof, if you will. They should be looking forward to spending their golden years together - not hiring attorneys and traumatizing their kids and their kids' kids.

But experts I talked to yesterday say that this kind of thing happens all the time, especially now that so many people are living longer.

"Besides empty nesters, the people who get divorced after 40 years are the ones who got married after they just finish their prom," said Whitney Casey, relationship insider for Match.com and author of "The Man Plan."

"If we waited until we're 40 to get married, we'd definitely stay married past 80."

After all, most people evolve and just aren't the same at 21 that they are at 60, which is what Casey suspects is behind the Gores' trip to splitsville.

"That's why this is so amicable. This is an amicable parting of ways, a separation of souls . . . . These people have a wonderful future and a new adventure. I have a great feeling that Tipper is looking forward to this new time in her life. He's going to go save the polar bears, and she's free to cuddle up with a teddy bear at home. That's hopeful for them."

Donna Tonrey, licensed marriage and family therapist and director of La Salle University's Marriage and Family Therapy master's program, said that she's seeing more late-in-life couples who are calling it quits the way the Gores have. "It's because of issues that haven't been dealt with," Tonrey said. "One can be poor communication. It can be a lack of intimacy, being able to share things and feelings. Sometimes it's emotional abuse. Sometimes people settle. Sometimes it's financial. The problem is, if the couple hasn't addressed the issue, they tend to build and build and build.

"What I'm seeing more often are couples coming in that have been married 25, 30, 35 years and then they're addressing the issues that have been in their marriage all along. . . ."

Also, aging can jolt unhappily marrieds into realizing that they need to act if they think they'll be happier with someone else. Stephanie Buehler, a psychologist and the author of an upcoming book titled "Sex, Love, & Mental Illness: A Couple's Guide to Staying Connected," wrote in an e-mail: "In my practice as a sex therapist, I see couples break up after many years of marriage due to sexual frustration. One partner loses interest in sex and the other still has a drive. They are unable to reach a compromise on their own. Usually, they have had many, many fights about sex, but also other topics as well, as the sweetness has been drained out of the relationship."

Send e-mail to heyjen@phillynews.com. My blog: http://go.philly.com/heyjen.