That's a very difficult question to answer. I learn new things all the time as I tackle home projects or get into new hobbies I've never experienced before, however short-lived or extensive. I don't know whether I can refer to my newfound interests as skills, although many technically are and many people would argue from opposing perspectives. A lot of skills out there can be learned on-the-fly or it can be just another naturally easy set of tasks for someone, with almost no learning curve. I don't know.
How often do you replace your wristwatch, say based on the kart ten years?