This convo couldn't have been more timely.
I bought a 49" Sony X800series - Smart - 4K UHD television for our living room in March, 2018. We watched tv all day and evening yesterday with no problems whatsoever. I went to turn the tv on this morning to watch the morning news... and wouldn't you know it? No power light, no picture, no sound. My grandson said, "Grandma, I think your tv is broken". I have some instructions for booting/powering on the tv when it has glitches, no sound/picture, etc. They've worked like a charm in the past. I tried twice to get it going and nuthin'. Nada. It's deader than a doornail. We watch a ton of tv. If we're awake, the tv is on. After 5 years, I'm sure it had reached it's end of life.
I have a bare bones 32" flat-screen Sony that I took out of a spare bedroom and set on top of a console table situated beneath the dead tv. It's not a smart TV which will take some getting used to but at least it's watchable. Since we have a temporary solution, there's no longer a sense of urgency to run out today and buy a new one. We'll get one sometime in the next few weeks.