Just completed Camino Frances
last month from St Jean. 4 kms per hour is just about right... I'm 75 years old, but fairly fit for a person in his dotage. I'd leave mornings about 7 or s0 - stop at the first sign of cafe con leche, then go another 1-2 hours to a 2nd breakfast (bocadillo or tortilla and coke or coffee), then usually around noon I'd see someone I knew along the way and stop for a convivial beer or vino tinto & another snack, then push on for another hour or so - by then it would be 2-3 or so... and I'd be looking for the day's albergue. Before I knew it, I'd hiked 5 or 6 hours and felt just fine. Lo day was about 16 kms - longest was 38km(I was toast by the time I reached Ponferrado).