My first proper road trip covered about two and a half thousand kilometres in ten days and I remember almost none of it, because I spent the whole time driving.
Every one since has covered less ground and been better. The variable that matters is not distance, and the planning tools all optimise for the wrong thing.
The number that matters is hours, not kilometres
Route planners give a driving time and it is always optimistic. It assumes no traffic, no stops, no navigation errors, and it does not include fuel, food, or anything you stop to look at.
My rule now is to take the estimate and add sixty percent. That has been accurate across a lot of trips.
Four hours of estimated driving is a full day once you have stopped twice, eaten, and looked at two things. Anything above that and the day becomes a transit day with a place to sleep at the end.
Three hours is the comfortable ceiling
Estimated driving time per day, for a trip that is supposed to be enjoyable.
That leaves most of the day for the reason you are there, and it means arriving somewhere with the energy to go out.
The alternative — five or six hours of driving daily — produces a trip where you see a lot of road and arrive everywhere tired. This is the mistake nearly everybody makes on their first attempt, and it is driven by trying to include too many places.
Two nights minimum, wherever possible
The change that improved my trips most.
One night somewhere means arriving in the evening, sleeping, and leaving in the morning. You have not been anywhere, you have slept in a different building.
Two nights means a full day with no driving, no packing and no checking out. It is the difference between passing through and being somewhere.
It also creates slack. A day with no driving absorbs a delay, a mechanical problem, or bad weather, none of which are recoverable in a schedule of consecutive single nights.
The route is not the interesting part
Motorways are efficient and identical everywhere, and they take you past places rather than through them.
The secondary road adds time and it is the trip. Villages, changes in landscape, the ability to stop when something looks interesting.
The compromise I use is motorway for the boring section and secondary roads through anywhere I actually want to see. Route planners will not do this for you and it takes about twenty minutes with a map.
Worth knowing: mountain and coastal roads take substantially longer than their distance suggests, sometimes double. Planning those sections on distance is how people end up driving in the dark on unfamiliar roads with drops.
Booking ahead or not
The argument goes both ways and my answer has settled on partly.
Book the first and last nights, and anywhere that is popular or has limited accommodation. Leave the middle open.
Fully booked means the route is fixed, which removes the main advantage of driving. Somewhere turns out to be better than expected and you cannot stay, or the weather is wrong and you cannot change plans.
Fully unbooked is fine in low season and stressful in high season, particularly arriving somewhere at seven in the evening to find everything full.
The practical things
Check what your insurance and breakdown cover actually cover in the countries you will drive through, particularly if crossing borders. This catches people.
Find out about tolls and how they are paid before you are at a barrier. Some systems require a device or a pre-registration and cannot be paid in cash.
Check the requirements for what must be carried in the vehicle, which vary by country and are enforced. Warning triangles, high visibility vests, breathalysers and spare bulbs are all mandatory somewhere.
Download offline maps, because signal is not reliable in exactly the places where navigation matters most.
And know where fuel is scarce. Long stretches with nothing are common in some regions and running low is avoidable.
Who drives
Worth planning rather than leaving to happen.
If two people can drive, alternating by half-days keeps both fresher than alternating by day, and means neither person spends a whole day as a passenger.
Make sure the second driver is actually on the rental agreement, which is a boring administrative point that invalidates the insurance if missed.
And if only one person drives, plan shorter days than you otherwise would. The driver is working while everybody else is on holiday, and that difference accumulates over a week.
What I do now
Fewer places, longer in each, three hours of driving maximum on any day, two nights everywhere, secondary roads for the interesting sections, and one entirely unplanned day in the middle.
The last one is the best thing I have added. A day with nothing booked and nowhere to be is where most of what I remember from these trips has happened.