Never. I have a life. I can live without a new device for a couple weeks. My 4S was good enough two weeks ago, it'll still be good a few more weeks from now, until supplies are in stock.
Seriously, do people have nothing better to do? It's just a phone people. No one is going to give a darn in 3 weeks that you were the first in line a had it a few weeks before everyone else.
(and for the record, I've owned a iPhone 3G, 4, 4S and and iPad 2 & 3, and I'll probably buy the iP5 so save your Fandroid/hater comments)
You wait in line for the experience. Like waiting in line to see a concert, movie, play, ride a ride at an amusement park; sure you don't have to, it will still be there when the line dies down, but to wait in anticipation for something with others that are equally excited, that's why you camp out and wait. Plus, you get to meet some cool people sometimes.