I think any program has a risk of "dying". How long does it have to be around before the risk is considered minimal? 5 years? 10 years? Chase UR has been around a few years already and seems to be growing, not diminishing. No, you're never going to have zero risk of it becoming a ghost town, but Chase seems committed.
For the Diner's Club example, even though it's not as active as some of the other forums anymore, does that mean it was never helpful at some point?