Screen has lines in it after its warmed up, color fades

Cause of screen burn typically is pixels are no longer showing full range of color. Typically a shop would cycle screens or blocks of very bright colors alternating colors to unstick any pixels not showing full range of some color. Setting tv back to factory default then adjusting could help also turning up brightness. Change color settings from cool to warm could help. Could also be a refresh rate. Verify tv is set to display at same rate as input device like cable box set to output 1080i while tv native is 720p. Just because there is a pic doesn't mean they are synced.if tv has to convert signal from 1080i to 540i then resize to fit 720p tv it may slow refresh rate tv is trying to display progressive scan image but not enough data is coming in so it redisplays previous image on every other line.and new data on every other line.
solution is check output video settings of source to match native resolution of tv. Hd cable box this is common as tech sets output to high resolution 1080i most inexpensive tv are 720p

If you wish to get some details; visit the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/
Line faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent. Faults to all LCD & Plasma screen are similar, irrespective of its brand and screen size.

To have a fair chance to advise or help I need to know the model number and brand of set(JVC)?

bad convergence ic's

this thing happened in my laptop also i got green screen fully
then when i hit it behind the screen it was gone but comes many times then again i would hit
later on the screen was completly lost then had to replace the screen
yous is a starting period so go to a nearby computer service and fix the screen

CRT's (tubes) are shot.

Are they thin, white lines running east to west? If so, they are called retrace lines and indicate that the screen settings for the picture tubes is set too high or there may be a mal-function of the CRT driver circuitry. Try adjusting the screen controls which are located behind the front grill of the TV behind an access panel. Once you remove the grill and access panel, you'll see a small control assembly the has two sets of controls. Three for adjusting the red, green, and blue focus, the other, the red, blue, and green screen controls. To adjust correctly, put the TV on an unused input(dark, blank picture) and adjust until there are no visable retrace lines or color in the image.

michtech

take the phone and have the LCD replaced on the phone.

I got this Sony KP-57WS500 57 in TV for FREE from a guy posting it on craigslist because he saw "BLUE SWIRL LINES" also knows as "Retrace Line" on the screen and he went to several repair people and got high repair costs so he was giving it away for free, but i found a guide that tells you how to adjust the tv to make the blue or green or red lines go away, aparantly the line show up because the voltage on the color ray gun tubes that get out of adjustment. Here is the Link to the REPAIR GUIDE. http://www.somelifeblog.com/2007/06/sony-projection-tv-red-line-repair.html

I would have to say it does sound like the CRT is reaching its end. The thing that points this out that the picture gradually gets a little bit better as it warms up. It most likely isn't worth the cost to fix it.