Each of our Shopify themes has its own changelog file available, and you can see them any time from the "Changelog" section (the last section), on this documentation.
Usually, we provide an update for our themes once a month. At the moment we do not notify when we release a new theme update, but this may change in the future.
To update our Shopify themes, please install our latest theme version from your Shopify admin, and you should see both theme versions available as in the following screenshot:
Next, on your old theme version, click on the "Actions -> Edit code" button. From the search input box find a file called "settings_data.json" which is under the "config" folder. This file is responsible for all the changes you have made to your Shopify Theme Customizer.
Copy the content of the file and paste it on the same file on your new theme version.