At what point does a temporary structure or feature start to require permanence? Consumer apps have the toothbrush test: is it used twice daily, consistently? If so, the app has achieved the near-impossible and embedded itself in the user’s existence. Along the way, it usually moves from being buried in a menu to the prime real estate of a home screen or shortcut bar.

In the physical realm, think of garden furniture. The season dictates when it’s brought out and kept ready for quick, ad hoc use, and when it’s packed up and stuffed in a shed. Without storage, it might go to the dump, with the intent to re-buy next season.

I suspect the temporary-permanent threshold is a function of how often something is used, how long each episode lasts, and how long it takes to stand up and stand down. More precisely, it’s the equilibrium between two costs:

• Permanence carries a holding cost: space, upkeep, and the opportunity cost of whatever else could occupy that spot.
• Temporariness carries a switching cost: the effort of setting up and packing away, paid every episode.

Three factors complicate the picture, though:

• Friction: making something permanent lowers its setup cost, which raises its use, which then justifies the permanence.
• Urgency: a fire extinguisher is rarely used, but a slow setup at the moment of need would be catastrophic.
• Defaults: many temporary things become permanent simply because nobody pays the teardown cost.

So perhaps the heuristic is to make temporariness the strong default and set a high bar for earning permanence. Take the allure of van life. Renting one for several distinct weekends won’t reveal everything about the lifestyle change, but it’ll reveal enough to make an informed decision about committing.

Another way to think of it is Dan John’s observation that “everything works—for about six weeks.” Novelty flatters anything new, so don’t commit to permanence until the equivalent of six weeks has passed and the novelty has worn off.