Perspective and TVs, how far away do you sit?

Ideally, you should always be close enough to your TV (or it should be large enough) to require you to actually move your head to follow action on-screen, i.e. it should take up the whole of your peripheral vision.

This is the principle behind IMAX and nothing less really allows for full immersion.

That said, this is almost impossible to achieve at home. You can do it with huge DLP screens, but the "screen door" effect is a big issue at those distances.