I bought a license quite a while ago. If i remember correctly this was a lifetime license.
However a few days ago I noticed that I was not able to update the theme on wordpress.com. And I saw on my account history here on this site that the license expired.
From the past few months, we changed our policy and make all our product lifetime validity. The users who purchase our product long back( i mean before policy changes ) we provide then lifetime validity too if they send a query regarding license.