In a response to a post from the AntiDRM Twitter account, Ubisoft Support has clarified that users who don’t sign in to their account can potentially lose access to Ubisoft games they’ve purchased. The initial post from AntiDRM featured a snippet of an e-mail sent to a user from Ubisoft notifying them that their account had been temporarily suspended due to inactivity and warning that it would be closed permanently in 30 days. Responding to the ominous e-mail, the Ubisoft Support Twitter account stated “We certainly do not want you to lose access to your games or account” and noted that account closure could be avoided by signing in to the account again.
https://store.steampowered.com/subscriber_agreement/#10
Read 10.C. Valve can do it any time.
Most likely other storefronts have similar clauses
10 doesn’t have a c. 9 is about account termination and has a c but there’s no mention of account deletion due to inactivity. “[if] Valve ceases providing such Subscriptions to similarly situated Subscribers generally” can be interpreted as encompassing subscribers that have been inactive, but it sounds more about when a game’s servers shut down or valve stops distributing it in a region and all players lose access.