...I guess you never forget how to inject sea urchins.
When I went back to my job a few weeks ago after a six month break, I'd forgotten where certain equipment and chemicals are stored, and phone numbers and the proper steps of certain procedures and even a name or two. I asked everyone why there was no light in the cold room and had to be reminded that its light switch is on the outside-- stuff like that. (Aren't they glad they rehired me?)
But what's as fresh as ever are the techniques. Anything that was hard to do at first, anything that took months of practice to really learn, is as intuitive now as if I'd never been away. It was very tricky, when I first learned, to stick a microscopic needle into a tiny sea urchin egg, inject some volume of BAC, yank the needle out, move the plate up, and stick the needle in the next egg, but eventually on a well-rowed plate I was doing about two eggs per second. Then the first plate I injected after coming back was done start-to-finish in eleven minutes, which is exactly as long as I used to take.
So it seems that information can leak away but acquired skills stick.