I used the Navy Data and put the full moon date and time in a spread sheet for the years from 1990 to 2001. I used the first full moon of each year and counted up the number of full moons during the year. Subtracted the Jauary current year from January full moon date-time next year to get number of days-fractions then divided by number of full moons for the year to get an average. The calculations took into account leap years by adding an extra day as needed. I don't see a slowing down trend when taking into account all the years 1990 to 2001. In fact the trend is a bit toward shorter time. The black line is the trend line determined from all the data points. It is a feature of Excel to be able to have it calculate a trend line. Apparently it is normal for the moon to speed up and slow down over a 10 or so year period of time.
Offered by Mike.