Just getup in the morning eat breakfast , ride till lunch , eat lunch , ride till four or five,
have a cuppa tea in your campsite , cook dinner or make another sandwich.

go to sleep , wake up the next morning and repeat..

forget mileage goals, enjoy the journey absorb the scenery , if you don't get the 600 miles, on day 6, so what ,
cover the rest of the miles in a bus or load the bike in someone's pickup truck.