I don't see why Hughes can't get a guy who is 30-ish, like a Bennett, who will be 29, for the long term as an example (I'm not saying Bennett, per se, will agree to sign with Montreal, just talking about the age and the impact such a player might have), or a Duchene as a stop-gap short term addition, who is still fast and still producing near a PPG pace, even if he will be 34 at the start of next season, or some other option that might be available, but a bit older than the actual core?
Another C, younger than the actual core average age right now, might well become ready to complement the current core as the immediate future 2C starts to dwindle.
Actually, all your players being the same age rarely happens and it becomes that much harder to keep them together.