store.steampowered.com/subscriber_agreement/
TERM AND TERMINATION
A. Term
The term of this Agreement (the “Term”) commences on the date you first indicate your acceptance of these terms, and will continue in effect until otherwise terminated in accordance with this Agreement.
B. Termination by You
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C. Termination by Valve
Valve may restrict or cancel your Account or any particular Subscription(s) at any time in the event that (a) Valve ceases providing such Subscriptions to similarly situated Subscribers generally, or (b) you breach any terms of this Agreement (including any Subscription Terms or Rules of Use). In the event that your Account or a particular Subscription is restricted or terminated or cancelled by Valve for a violation of this Agreement or improper or illegal activity, no refund, including of any Subscription fees or of any unused funds in your Steam Wallet, will be granted.
My reading of this is that licenses for sales (i.e. not subscriptions) are perpetual and will continue beyond the existence of Valve as a legal entity. Further Valve can’t revoke this license at their discretion, but only if the customer has been found to violate the platform ToS or Rules of Use.
Of course many publishers add their own EULA to the sale so that may vary from title to title.