jdillingham

I usually take my cue from who I am playing with.  If everyone wants to ride I ride, if they want to walk, I walk.  Unless the course is particularly hilly or the green to tee distance is overly long, my first choice is to walk.
 
Having said that, I live in Seattle and we have a lot of cart path only days, who wants to ride then?  Not Me.  I would say between October and May 95% of the time it is cart path only.  Most of the time it is because the ground warrants it, other times because the greens keepers are idiots.   Here we are past the middle of May and all the courses in the area are "cart path only".  So I walk.
 
Now I am leaving for a tournament out of town, we are going to play 8 rounds in 5 days.  I always ride during a tournament.  Also I find when I play a lot of back to back days or particularly back to back 36 hole days, it makes a little more sense to ride.  It has been about 5 years since I walked 36.
 
Also, a number of golf courses I play out of town in places like Hawaii and Arizona, they usually won't let you walk.  If you walk in AZ from June to September, the heat could kill you.
 
I started playing when I was 9 and I will be 66 this summer, I played several years before I even saw my first golf cart.  We walked all the time.