Hey Adam,
all my theme updates are free for all buyers ;) you can download the latest version of a theme from the “Downloads” tab of your ThemeForest account. Updating will not affect the content of the website, yet in case you’ve made changes to the theme files, they will be lost. For a safe way of altering the theme files, I highly recommend using child themes; a child theme is also included with Kanso (the “Resources” folder of the primary downloadable archive).
Sincerely,
Andrii / Satori Studio