if you wanted to drive i40 between OKC and Little Rock, you would be out of luck (unless you divert to Dallas).
That particular trip is a close one. Driving at a slower speed (60mph?) in a LR M3 you should be able to get from OCK to Little Rock (350 miles) in 5:50. That
range depends a lot on the weather though.
If you divert through Tulsa to use the Supercharger (why Dallas instead of Tulsa?), you add 48 miles to the trip. At 80 mph this leaves you 49 minutes to charge up in Tulsa for a break-even total trip duration. In this case, whether the
time it takes to charge up in Tulsa is more or less than 49 minutes will depend a lot on the weather.
With bad weather, you may use more battery on the way to Tulsa (requiring more charging time), however, in that weather, you might not have enough range at 60mph and would need to drive even slower to "skip the supercharger". As such, using the supercharger might still be faster than the direct route (the two routes will be really close in duration, but the Tulsa diversion will have a lot less range anxiety).
With good weather, you may use less battery on the way to Tulsa (requiring less charging time), however, in that good weather, you might be able to drive a bit faster than 60 mph and still "skip the supercharger". As such, the direct route might be a bit faster than the diversion (the two routes will be really close in duration, but the Tulsa diversion will have a lot less range anxiety).
So, depending on weather, it
MIGHT be a minute or two faster on a 6-hour trip to "drive slower and skip the supercharger" in some circumstances, but, really, it's practically the same amount of time and stopping to charge will provide a lot more "wiggle room".
All of these issues are of course covered in Tesla's coming soon map.
Agreed. If they build just 1 of the 3 superchargers that are planned along that route, it will make a huge difference in your ability to drive the I-40 path and charge along the way (cutting up to half an hour off the travel time). In that case it will absolutely NOT be faster to drive slower and skip the supercharger.
If they ever get around to building them.
We can only hope.