Three years ago (or thereabouts) it was formalized in CG Aviation...a section called "Strategic Napping" was thrown in our 3710 w/ criteria, i.e., min altitudes, max time sleeping, etc. The Chuck-130 is the only community that does this (as around 14 hrs is our max endurance), so I have practiced this on many all-night flights looking for migrants.:sleep_125
A case of regs catching up w/ actual practices.