I don't see how anyone can knowledgeably answer your question. There is a different dynamic this time around because Apple isn't doing online preorders of the 5s for delivery on the 20th. There's no doubt Apple wants long lines to drum up excitement and cause people to ask what people are waiting in line for.
Get there as early as you feel comfortable doing so. Last year, I got to a Verizon store between 6:00 and 6:30 AM and was number 7 or 8 in line. But that's when there were online preorders for the 5 that were being delivered on launch day.