If you’re lucky, you’ve managed to hang on to your closest friends your entire life. The same kid who sat next to you in second grade eventually became the best man at your wedding and mowed your lawn when you got arrested/shot/cancer/fired.

Friends like that are hard to find and even harder to keep. A lot of relationships once based on mutual rapport go bad. Just look at the divorce rate for proof. But, for now, I’m more interested in friendship.

Not all best friends stay best friends forever. One guy might keep the faith and lead a normal life, while another slides off into drug abuse and prison. Time can be a brutal sifter.

Geography has a lot to do with it. It’s easy to stay friends if you remain in the same area. It’s harder to do if you bounce around a lot.

There were four of us in 1969. Teenage boys living in the same small Southern California town, going to the same schools, and attending the same church. We sometimes referred to ourselves as the Filthy Four, though I can’t remember why.

Anyway, we were tight. Closer than brothers if I recall correctly — which isn’t always the case, given the things I’ve done to my brain through the years.

Everything — at least for me — came to a halt when the Old Man was transferred to Utah’s Fort Douglas. I said goodbye to my co-conspirators and moved on to a new batch of friends 700 miles away.

The bond didn’t entirely break. We stayed in touch through bouts with the military, church missions, school, marriage and the occasional disaster. Missions separated us as far as geographically possible — Canada, Ireland, Colombia and Uruguay.

During those times, it was the vagaries of the Postal Service that kept us loosely connected.

J.R. • “Did you hear D.T. got hit by a car?”

D.T. • “It was G.R. Broke his leg.”

R.K. • “Nope, me. Arm. Fell down stairs at Jethro Tull.”

As time went on, the silences grew longer. Families, jobs, and time exacted a price on our connectivity. Years passed without anything more than the infrequent whisper from someone who heard that someone else had heard that one of us …

Some relationships die. Others just hibernate. Last week, from our scattered homes in Arizona, Wyoming, Idaho and Utah, a group email sprang up.

Suddenly, G.R., J.R., D.T. and I were communicating like the past 50 years had been but a moment. We argued, insulted and gleefully reminded one another of less-than-stellar moments.

The Filthy Four were back. Sure, a lot has changed. We’re all grandfathers. Some of us have retired. One had a heart attack. Another lost a finger, while someone else has had considerable reconstructive surgery.

The good news is that we’re still married to the women we originally chose because of their high tolerances for male foolishness.

But somewhere in our heads, we’re still the same sophomoric idiots who once benefited from a common friendship that left a positive mark on us.

I have to wonder if the few years when we were inseparable, helped get us through all the years when we weren’t?

Robert Kirby is The Salt Lake Tribune’s humor columnist. Follow Kirby on Facebook.