I got a 51" Samsung PS51E550 Plasma in 2012, and recently vertical lines appeared near the right hand side.
I searched online and found similar cases, and was surprised to read people saying Samsung had still been replacing their screens for free.
I contacted Samsung today to organise service for mine, and questioned and was told any TV bought since Australian Consumer Law was introduced (January 2011) will still be repaired by them for free.
I'm really impressed by this policy.
Don't expect Samsung Mobile to do the same though, I still have to lodge a fair trading complaint over a bad case with them…
i had a 42 inch plasma that got the lines Samsung replaced with as new 51" plasma a couple of years back no dramas at all.