"Online-only: This game will be playable until 2028-06-30"
This forces the publisher to put their money where their mouth is. If the game is successful, like WoW, by all means extend the time it's playable for. If it 'flops', you're on the hook to support it for 3 years, since you shouldn't be putting out made-to-fail slop.
You really need either a minimum term of support in law, or a requirement to publish a docker of the server into escrow, to be released if the company fails or decides to discontinue.
A one-day warranty would almost certainly run afoul of the EU's merchantability laws.
Edit: Misread the date (sorry, American here -- we write dates weird). However, the point still stands: selling a product to consumers involves some warranty of merchantability, and breaching that entitles consumers to refunds (and can even get the publisher in trouble with regulators).
I wouldn't be concerned with publishers going the "guaranteed playable until" route because there's already consumer protections that discourage this type of thing.