You might be surprised. New languages can teach you quite a lot more than simply a new syntax - there are concepts that will be present and visible in a new language or stdlib that you might not have encountered before, and constant exposure to unfamiliar territory helps to keep you in constant learning mode.
The idea isn't that you abandon your existing languages every year. Nobody will be effective if they're always working exclusively in a language they've just started with, but you can take lessons learned in a new toy language and apply them to your broader work as a programmer, even if you never use that language again.
The idea isn't that you abandon your existing languages every year. Nobody will be effective if they're always working exclusively in a language they've just started with, but you can take lessons learned in a new toy language and apply them to your broader work as a programmer, even if you never use that language again.