When I was in boy scouts, one of the scoutmasters suggested creating a packing list for camping trips. His key suggestion was to update the list after a trip, adding anything you’d wished you’d had, and thoughtfully deleting anything you’d brought but ended up not using. (Thoughtfully in the sense of not deleting your first aid kit just because no one had gotten hurt on that trip.)

I immediately recognized the value of the idea, but I never really put it into practice, mainly because I was no good at preserving the master list from one trip to the next. That problem was eventually solved by computers.

My oldest pack lists go back to 1992, when Jackie and I took a vacation in London and Wales. Our itinerary was complex, because we were driving to St. Louis and spending the night with my mom, and then flying to London from there, and reversing the process for the return home. The pack list for that trip has things broken down by stages:

• Worn to St. Louis
• Carried to St. Louis and worn on plane
• In carry-on
• In checked luggage
• Left in St. Louis, for return drive

The key, though, was that instead of making the pack list on paper, I put it in a file on my computer. Then, the next time I went on a trip, the file was still around. I used it as a starting place to make my next pack list.

I’ve kept the basic format for twenty years now—stuff to pack, sorted by bag. At first I editing the old list for each new trip, but I long ago started letting old lists hang around, and eventually came up with a file name format to include the destination, the number of days, and the season. When I’m planning a new trip, I can quickly look through the old pack lists, find one with some overlap in terms of season and duration, and then use it as the basis for a new list. Because text files take up essentially no space, I’ve let old lists accumulate (in a small way—I’ve got a dozen or so).

Those old lists came in handy again just recently, as we’re preparing to move into our summer sublet. As it happens, I have an old pack list for a multi-week summer outing in furnished digs: my Clarion pack list from 2001. I’m having to adapt it—I don’t need the books by Clarion teachers that I was bringing to get autographed—but it’s not only a good guide, it’s a tested guide.

I strongly recommend making pack lists, and then keeping your old lists forever. You never know when you’re going to take a similar trip.