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.
Part of my point is that you (likely) won't be able to learn new ways of doing things in just one year of study. After a year's exposure to the language, my Perl looked like a funny flavour of C, only with regexes in places (I'd learned regexes earlier, working with Vim and grep). I think it'll take well more than a year to get very much that's useful out of a language.
Found a typo in this node? /msg me