How beneficial is drafting/slipstreaming?

[TomT]

My life is more important that a few more miles of range! It's a stupid (and probably illegal in many states) practice!

 

[jlv]

We set the follow distance at 1 car length and let auto-pilot do the rest.

That setting is not in car lengths.

To adjust the distance you want to maintain between Model S and a vehicle traveling ahead of you, rotate the cruise control lever to choose a setting from 1 (the closest following distance) to 7 (the longest following distance). Each setting corresponds to a time-based distance that represents how long it takes for Model S, from its current location, to reach the location of the rear bumper of the vehicle ahead.

A reasonable write-up: https://www.teslarati.com/set-tesla-tacc-following-distance/

 

[GRA]

Tailgating is both unsafe and illegal in a Tesla, but you will be seeing legal and safe tailgating soon:

Are those 80,000 pound trucks tailgating each other? Soon it may be perfectly normal - and safe

If you look to the next lane and see two 18-wheelers roar past at 70 mph with just 10 yards between them, you'll probably think they are dangerously close.

In this high-tech age, that may no longer be true. In fact, it might be just the opposite, and it might even end up saving you money...

Assuming the definition of 'soon' is as defined by Tesla. Platooning will be fine once vehicles have the necessary equipment and comms to make it safe, and have demonstrated that it is sufficiently reliable. We're still a long ways from 'soon'.