Does the key expire?

Hi guys, Recently my site wont display the original recaptcha box anymore. And no matter how i change the code, it just didnt show. Then i applied for a new key pair, and replaced the old ones in my site. And it works. So my question is, does the key pair expire? If it does, when will it expire? Thank you so much! -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/1gYXIc9.