I have read a few comments about OLED tv's not lasting too long. The problem with LED sets is, I believe, the level of blackness. This is where OLED is much better however the LED manufacturers are now bringing out variations on the way they are backlit so that the blackness level is improved.
My Pioneer plasma is over 6 years old and has a lovely picture quality but is only 43 inch. It's difficult to know what to replace it with.
Jerry
Hifi: IPL transmission line floorstanding speakers, Squeezebox Touch, Denafrips Ares 11 DAC, DCB1 Pre-amplifier, Croft Series 7 power amp.
Custom Hifi cables HA10SE headphone amplifier and Hifiman HE-400 headphones.
AV system: LG 55B7, Denon AVR -x2300w receiver, Quad 12L (front) 11c Centre and 11L rear . Velodyne DD15 subwoofer.