The fastest return I've ever done after a transcon was 6 hours, which I did last weekend. PDX-SFO-JFK (PS business), arriving at JFK around 12:15 a.m. Spent the night in Manhattan and left JFK on the first flight (6 a.m.) to IAD, to catch the IAD-DEN flight on a 777 in C.

You can read about the trip here.

When we checked in using EasyChicken at PDX, all of the BPs printed (including the return flights) except for the last segment (DEN-PDX). Got this at JFK the next morning. I booked the flights online, and neither the Website nor EasyChicken gave me strange looks about the short turnaround.