TL;DR: I estimate my personal usage will be 20-30 half hour charges/year
Here's what my typical yearly trip routine looks like:
80-100 mile trips (160-200 miles round trip) 1-2/month
150-180 mile trips (300-360 miles round trip) 6/year
300 mile trips (600 miles round trip) 2/year
600-1000 mile (1200-2000 miles round trip) trips 1/year
I'm looking towards a Gen III sedan in 2016-2017 timeframe. Model S is well outside my comfort range financially, and Supercharger network will not cover my area until 2015. I assume Tesla will focus on delivering a 200 mile 50 kWh Gen III that can charge at the full 120 kW rate (2.5 C) in order to prevent swarms of slow-charging Gen III sedans from clogging up the Supercharger networks. Below I assume that Gen III can charge at 120 kW = 200 miles in 30 minutes.
My 100 mile trips would not require a mid-route charge. Many of these would be overnight trips.
180 mile trips would probably require 1 mid-route charge 50% of the time. Other 50% an overnight charge at the destination would be adequate. (3 charges/year)
300 mile trips would likely require 3 mid-route charges. (3 x 2/year)
600-1000 mile trips would likely require 6-10 mid-route charges. (10/year)
So figure for my relatively modest uses, I would need about 20 charges/year, perhaps up to 30 if I travel more frequently "for free" or if I'm being conservative above.
P.S. This seems like it would be better served as a poll but I can't find a poll option. I've seen other polls here, is it restricted from new users?