I gave a Panasonic plasma to a friend a few years ago. It is now 10 years old and going strong. Honestly, short of a complete failure, the only two things that would cause me to upgrade would be a radical new technology (4K is nice but not in wide enough use) or there was an annoying technical issue (eg. black levels or brightness degrading badly).
FWIW, I did pick up a 40" 4K for the bedroom. $900, an LG. I gotta say 4K does look good (well, *Netflix* 4K, so there are limits) but if you're going to buy a sub-$1500 TV, just remember, you're the product. The EUA which one is forced to agree to basically requires you to give up all your rights. The TV communicates everything you watch, when and how, to LG and their partners. Smart TV's are scary that way. I wouldn't get one with a camera or microphone either. Apparently the more expensive ones are priced to factor in the loss of revenue from the lack of tracking technologies, but if you want that privacy, make sure to research before you buy.