An expiration date could be hard to estimate, but a minimum level of support based on sales might be worth thinking about.

As I understand it, that's not the main focus of this initiative though. It's mostly about opening up dead games for stuff like private servers, so we are not forced to lose access to all the art within when the developer pulls the plug.

It seems like a relatively small ask to at least _allow_ hardcore fans to keep something alive. I can imagine publishers that have a great connection with their community (like Coffeestain) actually benefitting from handling stuff like this in a decent way.