Levels adjustment: permanent, or just playback?

[fibbingbear]

When processing video, I've seen AVIsynth scripts adjust the levels for PC (or in some cases, TV) use. Should the adjustment be permanent (i.e., part of the encoding process, like a smoothing filter or de-interlacer), or should the video's levels be untouched and only adjusted during playback?

I can see some benefits and disadvantages of both. Curious what people do in practice. Also curious if the conversion between PC->TV --> TV->PC is fairly lossless. Also curious if people prefer to store it in "PC level" format or "TV level" format.

[R3Z]

In short, i dont bother encoding levels changes into my streams. When playing on PC i change the levels on playback trhough the cyberlink decoder, otherwise its how it was intended on my TV.

[Adub]

My PC is my source for all video and my monitor is my TV. Metaphorically.

Basically, I use my PC for everything, but I don't adjust levels unless they were wrong in the first place. The only filter that I use is ColorMatrix.