Good point. On-trip accuracy will be a bit better as the site calibrates driving efficiency. For planning, probably doesn't matter as much to the OP since this is the first road trip.
Even though I'm a premium ABRP user, I actually don't always use it in-car...it is a bit clunky (this is one place where it used to be better than it is now). Live Supercharger availability is a killer feature though, so I do occasionally pop up ABRP just to see that. For me, popping up the native Tesla Trip Consumption display on a trip is sufficient to monitor progress towards the next charging opportunity. I occasionally pop it up to see if I am doing better or worse than the initial prediction and if I'm in danger of falling below my comfort level (5% or so arrival SOC). Normally I'll use ABRP to plan and determine that I can make it to a particular Supercharger that perhaps the car's nav may not think I can reach. But I'll navigate to that one anyway and keep an eye on the arrival SOC during the trip to make sure that I am doing better than predicted by the car (this is almost always the case). If I'm not seeing a comfortable enough improvement in Tesla's estimate I may pop open ABRP and/or go to the earlier Supercharger.
This is the kind of thing I am looking for:
View attachment 637825
I like to use ABRP to plan trips, but then rely on the in-car nav on the actual trip. (In-car will precondition the battery, and get the handy Trip Consumption graph that RTPEV went over above.)
I think ABRP is really good for running different what-if scenarios. To start, it usually gives you two or three options in its results, just like Google Maps. Then, you can add different additional stops for side-trips, to see how that affects charging.
My favorite feature is the ability to add a stop at a hotel with a destination charger, and then click the edit icon, add the destination charger's power and the percentage you plan to charge to, and finally hit Recalculate. It will re-plan your trip, based on what you think you will be at after the overnight in the hotel. I pay for Premium, because I want to support them, my wife and I have 2 different electric cars, and I like to save my plans. However, I think the ability to manually add charging at a stop is available in the free version, too, not just as a paid feature.
(Like many others have said about destination charging in other threads, you shouldn't count on a hotel charger being available, or in working order. Always have a nearby supercharger in range, just in case you need to use it instead.)
I have mainly taken in-state trips in the 8 months I've owned my Model Y, but I have successfully used my "hotel strategy" on a road trip to Chicago (~500 miles each way) during the week after this past Christmas. I've also been using it a lot to plot my first coast-to-coast road trip in March. (Not just my first coast-to-coast trip in an electric car, but my first coast-to-coast trip ever!)