Just back from a 24-day Model S adventure going round-trip from Reno to Boston (8099 miles), and I wanted to post these tips while they're fresh in my mind:
• Use rated miles and charge 20% more than you need normally; 30% if driving in heavy rain, headwinds, or running the heater; 40% if both heavy rain and headwind. Then add 6 miles per 1000 ft of elevation gain (or subtract 6 miles per 1000 ft of elevation decline. Try to make your last charge stop of the day a short one (75 miles or less) so that you don't waste too much time charging miles you don't need that day.
• Cold weather is not a problem (on average the heater shortens your range about 15%), but you do want to plug the car in overnight - even if only from a regular wall socket to retain the charge.
• Drive 60 on freeways and remember that with multiple stops at RV parks or public chargers, "The faster you go, the longer it takes to get there!"
• Get a copy of the KOA Directory (or Woodalls if you need to use non-KOA RV parks), and join the Blink and Chargepoint networks. The KOA parks are the most EV friendly and you can charge at 28 rated miles per hours versus about 18 at most 30A J1772 chargers. Some Blink chargers are restricted to 17A in AZ, NM, and possibly other places.
• Get the Tesla App for your smartphone so you can monitor charging remotely. I had breakers pop at a Blink charger in Bristol, TN and a dozen times at various RV parks (it usually happens in the first hour). In each case the App saved me - I went back to the car, reduced the current to 32A (24A in the case of switching to the second Blink charger), and barely skipped a beat. Some nights at RV parks I was too tired to wait an hour and see if the breaker would hold 40A, in which case I set the car to 32A and went to sleep.
• Make arrangements the day of travel, checking on the availability of 50A RV park slots as you go. Prepay overnight stays if possible, otherwise use late check-in to avoid the reluctance that many non-KOA RV parks tend to have with allowing EVs.
• Carry a regular 12-guage 100-ft 120V extension cord, as it can save you in a pinch. I used mine at hotels to hold a charge during cold weather overnights after charging up at nearby Tesla stores. Strangely enough, no one seemed to mind, even when I once draped it out a 3rd floor window. The conversation also quickly shifts to the car.
• Be realistic. You can do almost anything that gas cars do when on the Superchargers (I drove 770 miles from Las Vegas to Reno in a day), but when charging from 50A RV park 14-50s the best you can hope for is about 375 miles a day, and even then it makes for some very late evening drives. Set the limit at 300 miles if you want a "normal" travel day.
• It's a challenge finding hotels and RV parks that are close enough that you can walk between the car and your room. I solved that problem in several locations by staying in a KOA cabin (which requires bringing your own linens and towels). If you do that, be sure to request a deluxe cabin, which has running water and a shower/bath.
• Charging costs vary. Most common was a $10 daytime charge at KOA camps, and $20-$30 overnight. But many times I had to pay the full overnight rate, because I was taking a spot that could otherwise be rented to an RVer.
• Some KOAs operate shuttles to interesting tourist spots nearby, and these make great daytime charging spots. My favorites were the KOAs near Hot Spring National Park, Nashville, and the Grand Canyon.