Only reason thats 2 years is more valuable because its rare you move elite players (#1C or #1D and even #1W sometimes) with more than 2 years left.
Typically big market players are moved with a year or less left on their deal or simply walk in free agency.
As for the rumors a couple months ago, posters were asking about Ekblad but FLA fans kept asking why would anyone move a #1 RD with 5 years left unless he asks for a trade.
I can see why people are bringing up Barkov, 2 years left and FLA has done Jack squat since he's been here but he was named Captain, seems shy/reserved, not a big market guy and Zito has made sure to have a ton of money ready for him when due.
I'd put the chances of Barkov re-signing in FLA around 60% imo. Zito can renegotiate as early as 2021 off season. 8 years x $10 million, maybe slightly higher if cap goes up again that year.
But that's why franchise players are easier to acquire with 2 years left, not why the superstar himself is most valuable with 2 years left.
I can understand the argument that Barkov or Ekblad with 2 years left is tradable; Barkov or Ekblad with 5 years left is not. But that would indicate a superstar with 5 years left is more valuable, perhaps even too valuable to trade. Not less.