HDMI cords can be tricky. People sometimes think of them as "It either works or it doesn't" and that's not 100% true. It was never actually spec'd to be ok beyond 4.5 meters but people noticed it seems fine in certain situations even longer than that so they dismissed HDMI.org 's guidelines and went nuts. Some combos work, others don't.
Sure if you use wires that are very thick, i.e. low resistance, you can go very far. Another approach is to use in-line booster amps along the way or one of the newer varieties of HDMI wires with micro amps built into the plug itself which are bus powered from the electronics. Monoprice's Redmere series would one example.
I suspect you had a marginal signal all these years but lucky for you it happened to be just barely good enough to establish contact so you were never aware of it. Over time the metal contacts on the plugs/jacks gets less springy so the contact area decreases and in some instances there can be oxidation as well. The giveaway when this happens is people often report that if they break and remake the connection everything comes back to life...at least for a while.
You might want to consider one of these solutions I mentioned.
P.S. Anther giveaway that the signal is there, but too weak to be a reliable, bulletproof connection is that lower resolution signals like 480i/p work, but 1080P doesn't.
In A/V reproduction accuracy, there IS no concept of "accounting for personal taste/preference". As art consumers we don't "pick" the level of bass, nor the tint/brightness of a scene's sky, any more than we pick the ending of a novel or Mona Lisa's type of smile. "High fidelity" means "high truthfulness", faithful to the original artist's intent: an unmodified, neutral, accurate copy of the original master, ideally being exact and with no discernable alterations, aka "transparency".
Last edited by m. zillch; 06-07-2016 at 07:02 PM.