Most of the answers are theoretical, and the main consensus is that it is dependent on the skill and how it was acquired. Similar to the ‘you never forget how to ride a bicycle’ adage, crafts and activities that require extensive muscle memory to learn (and the least conscious attention to perform) tend to be the most durable. Many aspects of bookbinding and knife sharpening fall into this category, and these are some of the most difficult skills to initally learn.
It’s a great question, relating not only to the acquisition of craft skills, but the maintenance of them. Some answers in the article may contain seeds of argument for institutional conservators who feel they are trapped in front of a screen and need to justify bench time. But no practitioners were ask to self-report on their own experience, so I will ask myself.
Q: Jeff, how long does it takes to lose a skill?
A: I usually don’t subscribe to the idea that various crafts and skills sets are so different that there are isolated muscle memories associated with them. When I teach freehand knife sharpening, for example, I try to emphasize the relationship between sharpening and leather paring: the muscle memory that it takes to hold the knife freehand on the sharpening stone is closely related to the way you need to consistently hold the knife to pare. So in many regards, I think if you are active in some craft activity it can slow the erosion of neglected skills in another.
That said, when I was a kid I tried to learn how the juggle one summer. It seemed like hundreds of hours were spent, essentially in failure. But the next summer, I picked up the three balls and for some reason it just worked. Juggling may be pure muscle memory, since it primarily depends on how accurate you throw the ball. Now when I try it, I am not nearly as good, but can keep the balls in the air for a short time and suspect if I kept at it could return to a basic proficiency. So in this case, the skill is severely degraded, but not lost.
A dispiriting aspect of this question is that one’s intellectual knowledge of what constitutes skillful performance often increases during the time that the physical ability to accomplish this decreases.
Well worth reading other perspectives: “How long does it take to lose a skill?”