In the days of old (I'm thinking BeoVision Avant CRT etc..) a tube screen TV could be "relevant" technology for 10+ years. Now... I'd say that within 2-3 years the technology is outdated. So, a TV isn't a sound investment unless you buy it with open eyes and accept that if you keep it and get long term value, it'll be a dinosaur by the time you have...
I'm not quite convinced by this argument, Lee. I think it's changed again, in favour of a longer-term purchase.
Although CRT's did have a longer lifespan in the 80s/early 90s, this quickly changed with the launch of widescreen content in the late 90s, even for CRT users this made for a compelling experience (ie. 16:9). Then came HD. So these were huge jumps and go back to 1998. You had to swap out your TV fairly often in those days. The early HD TVs were dreadful. Remember the BV7-40 MK1?
These days you can easily live with a top quality HD TV (BV12-65 is an example) and a 4K Ecplise won't need replacing for a long time as 8K isn't going to be here soon. So you can buy a relatively modern TV (BV11-55 is another example) and you'll get a fantastic picture for a fairly long period of time. My BV12-65 is probably 5 years old now and still looks amazing. I don't feel compelled to upgrade so rapidly.