JP's piece is worth reading! That said, I'd have to ask if one makes that big print, the likelihood is it will be viewed in another environment from the booth used for proofing and your eyes will likely adapt to the illuminant. So the booth while not 100% is a good call because you want to ensure WYSIWYG which means some way to view a proof next to the display. That means some kind of booth that allows you to view the two side by side without light spill on the display. And of course, that booth's illuminant may be different than the display so once again, we play the adaptation game again. In the end, you want to know that what you see on the display and what comes off on a print, even at a smaller size is close. They will never match 100%.