Just out of curiosity, does it make sense the suggestion to watch the season 4 finale as series finale? (no spoilers, of course... just be vague )
I hadn't considered before the possibility of watching Deconstruction of Falling Stars last. In terms of the emotional content of the show and the storylines of our characters, then no, Sleeping in Light is the end. Deconstruction of Falling Stars also has some foreshadowing for season 5 that you lose if you move it to the end. But without giving away anything at all about Deconstruction, I can see an argument for moving it to the end. Maybe not on your first run through - as others have said, stick to the order in the DVD sets for that, but on subsequent viewings it might be interesting to see how it works at the end.
And yes, that does sound a little paradoxical, but you will understand after you've seen it