I think what the author intended is not for you to become proficient at a new language every year. Instead you should try a new language each year. Learn new ways of doing things and apply them to the languages you are trying to become proficient at.

For example, I have had a hard time getting my head wrapped around OO in Perl. So I picked up a Java book, I am a little more comfortable with a language focused on OO now I can go back and study OO under Perl. I realize that the implementation may be slightly different, but the concept is the same.