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Expires after one year later means you won’t be able to download files from My Account page of our site and also you won’t get any theme update after one year.
If you want support for one more year or theme updates for one more year after one year of date of purchase then you have to renew the theme.
You can download the theme on your system and save it, and if you install theme on any site, it will work after one year also.
Hope this clears you doubts, if you have any other queries do let us know.