I rapidly concluded long distance train travel is not viable.
On one occasion I had two days of travel booked, and the very first train was an hour late, which led to a missed connection, and that was it - there was no way I could make my next train, and I lost some hundreds of euros of booked tickets and accommodation, and the compensation offered - if I had the will power to fight through the incredibly hostile claims mechanism on-line - was 30 euro. I was also stuck, as I had left my origin (a long-term AirBnB) and the next place I would live was at my destination. Fortunately, I was in Paris, so I travel to de Gaulle and booked a flight to my destination (where it was then necessary to book a hotel for an night, as I was a day early); I paid some hundreds more euros to complete my journey.
Essentially the problem is that the longer a train journey, the more late it will be, and if you miss a connection, you can lose everything afterwards; but you have to book everything in advance, because the main train routes are fully booked if you try to buy a ticket on the day.
So it just doesn't add up.