Sony India — TV display comes on then switches off automatically.

I have a Sony Bravia TV 55' Model No KDL 55W950B.
Serial No 3250614 Purchased in Pune from ezone in 2014 for more then Rs 1L.
For last 2 months the TV display comes on and off at will.
When the display is there the picture quality and sound is good but then the display just switches off automatically.
I contacted the Sony help line in June, they opened the TV and said the Mother Board is finished and I should replace the TV.
My question is that if the Mother board is finished, how is the TV running perfectly at times?
Also I feel that the problem is of some lose connection that is deliberately not being repaired to push me into surrendering a very expensive TV for Pittance.
I have an LG TV that was bought in 2009 that is working perfectly fine till date.
I bought a Sony TV because of the brand name which is known for its quality and long life of its gadgets.
But the sad experience with this TV and inability of your technicians to identify and rectify the problem honestly is very disappointing.
Now I am stuck with a very expensive TV and bad after sale service.