A few more points on why the 70D is a good value and choice vs the higher spec batteries.
-look at Bjorn's video on cold weather driving. The largest battery drain in cold weather is warm up. Once the Model S and battery is warmed up, the efficiency decrease is not as severe.
-If you check out the range calculator on the website - driving at 70 mph in 0 degree weather with heat on nets you 180 on 70D, 205 on 85D. At 65 it is 195 vs 222.
-The round trip is 180 miles. With 70mph, 0 degree temperature, and heat on you'll be making a CHADEMO stop in the 70D for sure (which you have access to, removing a major factor). With 85D in these conditions, you only get a 25 miles in addition to that. That is perhaps an absolute 9-10% of the battery. You can make it without CHADEMO in those conditions technically, but do you really want to go without a charge with a low buffer? If I had an 85D I would still use CHADEMO and get better buffer. If you have a winter storm or bad road conditions, I would still hit the CHADEMO on both.
-if you CHADEMO the 70D for quick snack or lunch, vs no stop with the 85D you will have significantly more of a buffer than the 85D which does not CHADEMO charge for your 180 mile roundtrip
-The 70D will ABSOLUTELY do everything you need it to with your needs. It will do what you want. You have a little bit more flexibility and a little less need for planning with the 85D, not a major difference though.
-everyone should be taking driving breaks - perfect for a chademo charge, instead of driving 200 miles straight.
Why it's vital to take breaks while driving long distances - Telegraph
-the charging rate difference between the 85 and 70 batteries disappears when you take breaks, grab a snack or lunch. Part of my most recent trip involved driving near an 85. They stopped for lunch, I took a quick snack - regardless the charge wanted to reach the next SC was complete before I received my food. They were continuing to eat. Real world factors change the dynamic.
-in two years or so with much greater expanded Supercharger and Non Tesla charger access, bigger battery specs, the differences discussed between the 85D and the 70D of 2015 will be piddling.