We should not sit very near to the TV, At the same time we should not see the same from a very long distance also. Some specialists say we should maintain an 8 to 10 feet distance. But as a general who should maintain a distance of t times the width of the TV, you are watching. For example, the width of the TV is 32 inches, we should maintain a 32 X 5 = 160 inches distance which is equal to about 13 feet. In addition to distance, your sitting position is also very important. In addition to the above one should give a 20 second gap after every 20 minutes watch.
As this is a minimum ideal distance at viewing at eye level line, keeping the same in mind we can place the TV at different distances and heights and family members can make test views. Accordingly the seating or the TV placement can be adjusted to suit strain-less view, convenient and easy movement in the room etc. We have to keep theory and practical wisdom in an optimum fusion
However it is better to limit the TV size to 32 inches maximum in normal small rooms. But in larger living rooms and halls one can go for larger size TV too..
Knowledge is power.