Hello Raphael,
As our terms and conditions, once you purchase any of our extensions, you will have a subscription of 12 months to download updates and get our free supports. You can use the purchased extensions on any websites that you have.
After 12 months, if you don't want to update the extension, then you don't need to renew the extension. You can still continue to use the extension on your sites then.
By the way, what's name of the extension that you are interesting to purchase?
Sincerely, OS Solution Team.