I'm a novice programmer. I study languages such as C, C++, Python and Java (mainly focusing on C++). I'm what you'd call "young and inexperienced" and I admit that because I can't claim otherwise.
As a student, I have many other problems besides programming. I practice programming as often as I can, and especially because my teacher gives me a lot more exercises than the rest of the class (it's a very low level), so oftentimes I spend weeks doing something else such as school projects or sports, or traveling, anything besides programming.
Don't get me wrong though, I love programming. I love to build functional code, to watch as a program comes alive at the push of a button, and to learn as much as I can. The thing is, I simply don't have much time for it.
Straight to the question, now: does your programming knowledge decrease as time passes and you don't practice? You may ask "how much time do you mean?". I don't mean a specific amount of time, but for reference you could take a month-two or even a year as an example.
By knowledge I mean anything from syntax to language functionality.