Cory and I just drove 1200mi on the first half of a road trip not quite as epic as yours. Almost every supercharger we hit was empty. I think across those 1200 miles and 7 (8?) supercharger stops we saw a total of four other Teslas charging. Three of those were them pulling out as we pulled in, or vice versa.
The destination chargers on the other hand... way more problems with those. They tend to be close in to places, unlike the super chargers that are tucked away behind or way off to the side of places. I’m glad I’m not staying here just for a day. Both destination chargers at the place we are staying for the week we’re iced when we got here, the rest of that day and overnight and most of today. I finally got a chance to plug in today. Which was good, I got to see the snowflake on the battery gauge for the first time today!