Licences do not expire, but you should read the licensing terms carefully as some applications will need you to have to relicense (work for a different customer) or to use a different licence (like putting the asset on T-shirts or mugs).
Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).
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