The latest 7-man DTM statistics double the evidence that log(maxDTM) is increasing linearly with the number of men ... that is to say, that maxDTM is increasing exponentially with the number of men.
I give the detail on this in http://centaur.reading.ac.uk/34268/ ... and the graph can also be found in Tim Krabbe's excellent and recently revived Open Chess Diary, http://timkr.home.xs4all.nl/chess2/diary.htm, item #393.
The trend seems to be "Three more men: maxMate times ten!" , a conjecture which a recent visitor, Thomine Stolberg-Rohr WFM, dubbed "Haworth's Law".
As always, predictions can be premature - but the linearity of the trend is quite seductive.
g