@Servais I'd love to do this once, but this is not practical at all where I live in order to do it more often, because I live in one of the countries marked with a shade of red on this map (in S-E Europe). And that is not taking into account various incidents that can occur with the locomotive and/or other rolling stock.

Train travels inside the country are indeed doable, and many people take them, but the speed is so low that for longer distances it is rather more feasible to travel by plane in a couple of hours than take one full day for each trip.