Can I upgrade my license?
Yes, you can upgrade at any time by using the upgrade link in your account area. The price of the upgrade is the price of the new license minus the price you paid for your current license. The expiration date will remain the same and the price is not pro-rated.
When upgrading to an Ultimate license, the purchases of extensions are not factored into the price of the upgrade. So the price of the upgrade will be the price of the Ultimate license minus the price of the Gravity Flow license - not Gravity Flow plus extensions.
You can find the upgrade link in the Purchases section of your account. Click on the license you wish to upgrade.