Never keep sour cream in your refrigerator more than six years.  It’s a lesson to live by, along with avoiding ground wars in Asia.

I have learned this lesson the hard way, and I haven’t even been in the military, where they rarely use sour cream.

You’re probably wondering, as I am, why we felt the need to have sour cream at all, since it tends to be much more sour than ice cream and doesn’t come in pistachio. The reason that we had it, of course, was because it had been on special at the supermarket and you could buy one and get one free, even if you didn’t want the first one in the first place.

So we had two little containers of sour cream and managed, some time ago, to use most of the first container when we ran out of the two containers of gluten-free unsalted mustard we had bought at another buy-one-get-one free special and thought that sour cream would be a reasonable substitute.

But we didn’t need the second container and it just stayed there, moving further and further toward the back of the refrigerator, approaching the no-man’s land where no one in our family had ever ventured or received an email from.

It got pushed behind the leftover rice dish that was made with grapefruit juice when we ran out of water. It got jammed behind the remains of the birthday cake my wife had made to celebrate surviving Y2K. It was edged out by the extra portions we had saved of the tuna casserole we couldn’t convince our kids to eat even if we promised them that they would never have to eat it again.

In other words, it became part of the furniture of our house, a dependable touchstone like the smoke alarm on the wall that no longer worked or the metal turkey lacing skewers stuck in the sink trash disposal that made that grinding sound. We have grown accustomed to our little container of sour cream.  It was a member of the family we knew we could depend on to always be there.

Then, the other day, we realized we needed sour cream. It was late, sour cream stores throughout the community were closed, and we had a sour cream emergency.

My wife was going to make a sour cream pound cake, an old family recipe that she was certain didn’t belong to her family, but wanted to make anyway. We had all the ingredients, until we realized that the sour cream pound cake would need sour cream.

Fortunately, I remembered that it was right there, behind the container that could have contained lentil soup but that also might have been our daughter’s sixth-grade deviled egg class chemistry experiment.

We rearranged the refrigerator furniture and triumphantly brought out the sour cream. It was pistachio.