Of course, the route planning of a cruise itself depends primarily on how much time is available for the journey on board. If you really want to go on holiday, "eating up kilometres" should not be the goal. If you arrive too late (especially in the high season), at least the best berths are already taken and the shops ashore are closed (not to mention the sights).
Rest days and reserve days are also very important for safety: on the one hand, breaks are needed on longer trips, especially if the journey was exceptionally physically demanding, such as in heavy seas over a longer period of time. The same applies to concentration: A day inland with lots of traffic, strong currents and many locks also saps your strength.
On the other hand, the weather can quickly disrupt even a well-organised stage plan. If you have to travel every day to complete the planned route, you are putting yourself under unnecessary pressure - at the expense of safety. Even in calm weather, a series of very long days on the water can be exhausting, regardless of whether you are travelling inland or out.
Wind, direct sunlight and boat movements leave their mark - especially if a crew member is not regularly travelling with the boat. Six to seven hours per day should therefore not be exceeded when planning, even in this case including the reserve, of course. It can also be less.
