I was rightfully called out on the last graph - too little time and sloppy thinking.  Here is the distribution of my sleep recordings.  The purple bars show how what percent (of the 199 recordings) lasted within the six minute window of the x-axis.  The orange cumulative line indicates the percent of daily sleep less than or equal to the hours shown - e.g., 81% of days, I slept less than 7.6 hours.  Apparently I am a little more likely to sleep 6.2 or 6.7 hours than my average of 6.4.

Measuring 201 of the last 239 nights, the general trend is slightly down.  Average sleep is 6 hours, 22 minutes, with a standard deviation of 1 hour, 28 minutes.  Minimum non-zero sleep is 1 hour, 27 minutes, and maximum was 10 hours, 14 minutes.