Yes. You can purchase additional Flex Tokens at any time. In order to allow you more time to use your additional tokens, purchasing additional tokens resets your annual subscription term. Your new annual term begins on the date of the additional-token purchase, and your available tokens—including any unused tokens already in your account and the newly purchased tokens—remain available through the new expiration date.
For example: You purchase the Professional Plan on January 1, 20X7, which includes 20 tokens and expires on January 1, 20X8. On October 1, 20X7, you have 3 unused tokens and purchase 20 additional tokens. Your subscription is reset on October 1, 20X7. You now have 23 available tokens, and they remain available until October 1, 20X8, unless you purchase additional tokens again or otherwise change your subscription.
The price, number of tokens, and new renewal terms for any additional-token purchase will be shown before you complete that purchase.