We're in the northeast where superchargers are fairly dense, and thus 60D was probably going to be enough for us. If it turns out not to be the case, we can upgrade later to 75D for a minor penalty. That was a big factor in having the confidence to buy a "smaller" (software limited) battery.
We just did our first long trip of ~600 miles in the 60D, and SC availability was certainly not a problem. We never went below ~20% charge.
We don't know yet how winter temps will affect the range, but it doesn't get *that* cold here, near the ocean, and we tend to travel during the holidays when there is lots of traffic, so we should get a range boost just from going a bit slower.