Yes, it's normal. What you don't use you lose. When you need it, you'll be surprised how much will come back but don't expect to be as good as when you learned

Yes, it's normal. What you don't use you lose. When you need it, you'll be surprised how much will come back but don't expect to be as good as when you learned it. Is it worth relearning? Only when you need it. The big problem comes when you need to change jobs. If the industry has moved on from what you know then you'll have a hard time finding a job. What make sense is to stay aware of the industry trends and keep up to date.