If it is LG, some of them tell you how long it's been used for in the settings/information somewhere.
http
/www.tomshardware.co.uk/forum/all.html
You also got to remember, as Robert said, age, wear and tear, and of course, a 7 year old technology TV.
Even a modern cheapo would probably be better.
I just did a google and got this from Amazon
Customers who viewed LG 47LM4600 47" Class Cinema 3D 1080P 120HZ LED LCD TV also viewed
4.1 out of 5 stars 4,032
8 used and new from $158.50