For the record, there is some industry research on course length preferences among golfers, including the Growing the Game Study by Frank Thomas (former USGA Technology guru and currently an independent consultant) which you can find at
http://www.growingthegame.org/.
I have interpolated his data and some from other studies and expect the following division of play at most courses:
Course Length/Rounds (In %)
7000 3.5%
6600+/- 16%
6100 +/- 57.5%
5600+/- 19.0%
4900 +/- 4%
Clearly, most of us already have gotten this message. I was surprised by studies showing that senior men actually prefer courses under 6000K - I would have thought male ego would have kept that number above 6000.
I have clients asking me to do 7200 yard plus courses, but make the back tee a 15 X 15 square - which can be mowed in three quick passes, and is more than enough space for the projected 1000 rounds a year it will see - since it is so little used.
Of course, there is one simple solution to the whole playing the course too long problem - Good old fashioned scorecard lying! I have measured courses, and in addition to the old measure from the back rather than middle trick, many simply inflate their scorecard yardage by 8-10%. I think some also put their 150 markers closer to 140-145 to encourage proper clubbing, but that is a different story.