Nowadays people type a lot and don't handwrite very often as they once did. When you type in Chinese, you type in Pinyin which doesn't help remember the "spelling" of a character at all. And in English, it's like the more you type, the more you are of a good speller. Usually, however, because of the "muscle memory" (like the way you remember how to write your designed signature), characters won't be very easy to forget how to write, if you have actually written them for certain times. But still, it's very normal for a Chinese to forget how to write a complicated and not often used character. The good thing is that you will get a better memory of a character after forgetting it once, twice or more times in the past.