Yes, but you have to "keep up" by using these skills!
I spoke four (human) languages, but I completely forgot my German! I did not speak it for 20 years.
I spoke/write over 20 (computer) languages. Name it, I knew it!
IF you don t use it regularly, you WILL forget it!
I have to live in Germany for at least a week to "restart" speaking german.
I have to have a REASON to program something, then, the language of that program comes back, very quickly!
I was once asked to replace the programmer on a HUGE industrial site (Iraq, 1980). I learned COBOL in a couple of weeks! 20 years later, I was asked to do "the same". I was given a book, and in a week, I was back!
You NEVER completely forget what you have learned! They are in your head! You have just forgotten how to "access it".
You will retain your skills! You may just not be able to retreive them!
I realized that ALL you need is ... a "trtigger"!