I bought the 85kw battery based on several factors, after I originally signed up for the 60. My original thought was that I wanted to be able to use the supercharger system and I had to go from 40 to 60. The 40 was problematic because I often drive more than 100 miles in a day and although I'm close enough to the Hawthorne supercharger to take advantage of it, the 40 didn't give me that option. Once I was at the 60 level, and had to pay $2,000 for the supercharger option, it was easy to justify going to the 85 based on the unlimited mileage warranty on the battery. Although I've owned the car for 4 months, I've only used it for 3 months and have 8,000 miles on it. Here's my thought on overbuying.
For virtually everyone a 40 would be fine, but people don't realize that they're buying a car for 2% of their use, rather than the 98%. I have often thought that Tesla would sell more cars and eliminate vacation range anxiety if they simply said that the purchase price included 14 days of rental car for the typical 2 week driving vacation. If you can go back to an ICE for vacation, most of us could have lived nicely with a cheaper/lesser battery.
If I had saved $10,000 and gotten the 60, even at $50/day for a rental, I could have had 200 days of a rental. Over 8 years that means 25 days/year. And that doesn't account for the cost of money (present valuation)
With all that said, I like the option of getting from here to there in my 85 without stopping as frequently as if I had a 60. As the superchargers become more frequent and the charging time decreases with higher output, this will be less of a concern.
I guess after all this rambling, my point is that everyone should buy a Tesla. They should still make the 40 available and sell as low a priced car as possible. Instead of dropping the 40, they should make an effort to explain that a 40 is good for 95% of your use and a rental (even if you paid for it yourself) wouldn't cost as much as the money you saved on gasoline.