It takes 16 days to drive 8000 miles if you drive 500 miles per day.
Most people can safely drive 500 miles per day which is a safe distance before they get tired and fatigued and need to stop and rest for the night.
So assuming you drive 500 miles per day and that includes your stops for using the restroom, stretching, walking around, getting gasoline etc you could easily cover the 8000 miles in just 16 days.
To drive 5000 miles assuming you drive 500 miles per day then it would take you 10 days to drive 5000 miles.
If you drive 800 miles per day then you would drive the 5000 miles in 6 days and around 5 hours on the 7th day or assume it takes you 7 days which is a week to drive the 5000 miles in driving 800 miles per day.
In a car I've driven 800 miles in a day but it was very tiring but when driving a truck with my travel trailer I drive only a maximum of 500 miles per day.
So for me with my travel trailer driving 500 miles per day it would take me 10 days to drive the 5000 miles.
That includes stops for gasoline, resting, peeing, eating etc.
Some people can drive 1000 miles in one day which is really tiring for me and if you drove 1000 miles per day then you could drive the 5000 miles in just 5 days.
If you're feeling tired though don't try to push it too much.
Drive until you get tired and then pull off the road and rest.