If you're going on a 500 mile road trip you could easily and safely make the 500 mile drive within 10 to 12 hours depending on how fast you drive and how often you stop to take breaks.
Whenever I drive a 500 mile road trip I reach my destination within 11 hours which is a good time frame to get from point A to Point B going 500 miles.
So if it took me 11 hours to drive 500 miles and I wanted to drive 1,500 miles then it would take me a 3 day drive to drive the 1,500 miles.
I have driven 800 miles in one day but it's getting harder for me to do so as I get older.
But to drive 500 miles expect it to take 11 to 12 hours minimum but it could take you 13 to 14 hours depending on how often you stop to take a break and how long those breaks are.
You should stop to take a break at least every 2 hours on the road trip to pull over and rest and walk around and use the restroom.