I bought a Panasonic 42" TH5 in '02. Expensive. Still use it in another room, hooked up to a Freeview tuner. I just recalibrated it recently, and it looks excellent even by today's standards. I'll be using it until it packs in.
My current TV is a 2nd gen 4k set from 2014. TV before that was a cheapo Sammy 32". TV before that was a 32" Sony Trinton CRT data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7. It took 2 of us and a few beers to get it in the skip after it died.
As for the questiion...well when I feel the need to upgrade. My next TV will be OLED for sure. I was planning on getting a 65" B6 last year unfortunately the money had to go elsewhere!
I bought a Hitachi 32 inch Plasma in 2004 which cost £3500!Then upgraded to a Samsung 50" Plasma which was the first native 1080 panel whenever that was - probably 8 years ago.Waited until buying a new house in 2015 and upgraded to what I consider the perfect TV - OLED LG which is 4k and HDR so I can't see me upgrading again for a long time.
I also run an Epson TW9300 PJ which is a fake 4k projector so I definitely won't be upgrading my TV to a bigger one as the PJ picture, even at 100", is superb.
Got myself my first 65" 4K last summer after buying myself a nice flat which had a wall begging or a large screen. I hadn't bought anything for previous 6 years. I'll think about upgrading when I can get my hands on a 65" OLED for £2.5k
I only upgrade when there has been a significant change in technology, so for instance when flat TVs become affordable to reduce the space taken up by a monster CRT and more recently when the bezel reduced from around 1.5" wide to little over 1/4" wide, thus allowing a larger picture in the same space.
Due to me not having a room the size of that typically found in a castle, and that TV is a relatively minor means of entertainment compared with HiFi for me, I have no intention of having a screen greater than 40" which would dominate the room, and thus I am unlikely to upgrade in the foreseeable future as the defining factor for me is not so much the TV itself, but the poor quality of TV programmes, making the TV an even less important part of my living room.
Therefore the next upgrade is likely to be when this one breaks, and hopefully the industry by then will not have got totally carried away with size, and a reasonable range of 40" TVs will still be available.
I don't upgrade very often, about every six years but I do collect tvs and now have one pretty much every room of the house bar the bathroom but they tend to be cheap small sets bought in the sale.
For my main screen I like to see what's out there, wait until the tech has matured a bit and then jump in, upgraded last year to 4k with the LG UH661V, not the best but had a few features that were important to me, not least having a built in Freesat tuner, as someone who lives in a very poor Freeview area and who inherited a sky dish when moving in, Freesat has been my only form of over the air broadcast and I must say, it's a shame more people don't take advantage of it as the HD channels look much better than Freeview to my poorly calibrated eyes.
It used to be 2-3 years, but have not bought a new panel for the last 6 years.Main reason is diminishing advantage of doing so.I would not upgrade any of my panels (unless they fail) and they are only 1080P compliant - albeit top notch units.
I may however go to full 4K on my projector, but only when prices come down. (Currently JVC HD-1)
I doubt after that I will be inclined to buy another TV again.The real life benefits just are not there ... it seems this plateau in real life improvements in audio visual is quite real.
got a sony 32d300 years ago hd ready £1100 Matt Panel 10-bit BEST tv i ever owned !
Sony 40w5500 which was ok but backward step picture wise to D300 and it Bled every where !
Now i have a LG Oled C6 55 - Sad day for me to give up on Sony - but have to say picture is Very Good, most of my 1080p stuff looks better than 4k ? (eyes have been tested) best viewing angle & best 3D on any tv ever made including the E6/G6. Didnt care for 3D untill viewing on this tv.
Now even my 10 year old D300 had better color graduation much smother than the oled..but LG has pipped it. Also getting a new mattress some reason everytime i change the TV we get a new mattress , maybe a 800/1200 spring loldata:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
I tend to upgrade within 2 years. Currently own a LG OLED B6 which is great! (Especially having had it calibrated by Display Calibration).
I upgrade every five years or so. Current panel is a Panasonic VT60 but plan on purchasing an Ultra HD panel next year - either an OLED or whatever Sony replaces the ZD9 with.