The Model S and X are the only EVs that can do long distance traveling in a reasonable amount of time. Compared to an ICE car it takes about 20-25% longer for charging on the way. The shorter the trip, the less charging makes a difference. For example on a 300-400 mile trip, you start with a full charge, stop once at a Supercharger and then you can run the battery down to your destination where you (hopefully) have a charger. For 5-6 hours driving you would only have to spend maybe 40 min at a Supercharger.
The longer the trip, thought, the more charging stops you will need and the ratio between drive time and charge time is about 1:4 to 1:5. That's a significant amount of time on long trips. One mistake a lot of new owners make is to charge to a pretty high level mostly out of uncertainty how much they will need to make it to the next Supercharger. While this is safe it slows you down overall significantly.
Superchargers are fast, but the charge speed depends very much on the state of charge. IOW, how much is left in your battery when you arrive has a big impact on how fast it'll charge.
Here are some number that show how big the difference is. Let's say you arrive with 0%.
In the first 10 minutes you will gain 70 miles
in the next 10 minutes you will gain 46 miles
in the next 10 minutes you will gain 36 miles
in the next 10 minutes you will gain 29 miles
In 40 minutes you got 180 miles. The average is 4.5 miles per minute
Now lets see how the numbers look when you arrive at 30% battery left.
In the first 10 minutes you will gain 29 miles
in the next 10 minutes you will gain 27 miles
in the next 10 minutes you will gain 20 miles
in the next 10 minutes you will gain 18 miles
In 40 minutes you got 94 miles. The average is 2.35 miles per minute
The difference is huge! Almost twice the speed when you arrive at 0% vs 30%!
Now of course it's not very good for the battery to run it down to zero. It is also very stressful on you and if anything goes wrong, you have absolutely no buffer. You should always allow yourself a buffer. But just from a time point of view, you should aim to arrive at the next Supercharger at a low state of charge to significantly cut down charge time.
I remember a trip where I met another Model S owner going the same route. I arrived 15 min later than she did at the first Supercharger with almost zero on my battery. I charged just enough to make it to the next Supercharger. It was 100 miles away, but I charged to 150 knowing I was going fast and had head wind. I left the Supercharger before the other driver. I arrived at the next Supercharger with 10 miles left. Again I charged just enough to make it to the next one. As I was done charging and pulled out, I saw the other driver pull in. Not only did she charge much more than she needed at the previous Supercharger, she also arrived at a high state of charge slowing her down again. Over a 200 mile distance I gained aprox one hour over the other driver. Same cars, same driving speed, same conditions. Just by optimizing the charge speed.
Again, I don't advocate to run your battery down too low. My message is: don't add in a big buffer just to be safe and then drive slow on top of it. It'll slow you down a lot. As I said in the beginning, it won't matter much on trips where you only have one or maybe two Supercharger stops. But the longer the trip, the more it makes a difference.
Use the trip energy app. It will predicts (based on your driving and the conditions) how much you will have in your battery when you arrive. Keep an eye on it and use it to aim for a low state of charge without risking anything. It's very useful to optimize your trip.