Hello, I'm TV Tech1 and I'll be working with you to identify and help you resolve your problem.
It's hard for me to pinpoint life expectancy of LCD TV sets, because they are basically too new to do that. While engineers claim 50,000 hours, that's a TV in a perfect environment, and really the "Parts availability" is what truly limits the lifespan of a TV set. So overall, you can expect about 10 years of serviceable lifetime with parts, and the boards will usually give you about 15 years total time, and failure rates...that's about 5-8 years before the TV requires a repair.
Now, looking at your blue vertical line, it can be caused by several different sections of the TV set, from the video board (unlikely) to the TCON or the TV's ribbon cable ICs that we call TAB ICs (more likely with single lines, up to a two inch wide vertical band ).
The test we run...we turn on the TV menu and hopefully the line falls within the display area of the menu. Then we can see if the line shows up in the menu or behind the menu.