So I got in bed at one this morning, and conked out readily . . . then woke up again at six in the morning, on the couch.  I have only one memory of the intervening time: pulling blankets up on the couch because I was cold.  It was probably also the fact that I was laying on a comfortable couch with blankets that put me to sleep so quickly.  This morning, I had a random youtube video paused at about seven minutes, so I figure with time to get to the couch, situate myself, and pull up the video, that gives me at least ten minutes between my nap and my sleep, and probably closer to fifteen.  

I guess my body clock kicked in, because I woke up on my own a little after six and, although rather groggy, had the sense to not go back to sleep, after I'd slept for about four and a half hours.  I'm lucky that happened; if I'd slept until eight or later, I might have had a problem.  As it is, I only slept for half an hour longer than normal, and woke up two hours before I normally would, so I think I'll be okay.  I almost fell asleep this afternoon when Bryon took a nap, and I consider that to be a good sign.

I'll post again after my 10 pm nap.