Many, many places I have been to open up at lunch time and operate until sold out then close. Some I have seen have lines that span over a block long, other move quickly so there is not an extremely long line.
Many of these sell by the pound as they do not have a lot of seating (some have no seating). This also helps to move the lines as they are not making sandwiches and or platters.
Humphrey's DownEast Beast W/BBQ Guru