Longest journey (both distance and time) on a single train was in 1963 on the return trip of a school holiday to Germany to Austria. We left Wien Westbahnhof in the rearmost coach of a very long (15+?) train at about 23:00. Sleeping overnight in the couchettes we crassed into Germany at Passau, and picked up the Rhien route at Mainz. There were several reversals at 'kopfbahnhofs' (the town/city stations that did not allow through running), and at many of them coaches were removed from what was started as the front and others attached to the rear. By the time we arrived in Oostende for the ferry (about 14:30 the next day), our coach was second from the front - travelling in the same direction that we started. There were several loco changes (ÖBB electric to DB electric, DB electric to Steam at Aachen and Steam to SNCB Electric at Liége for the final run to Oostende). There were obviously other changes at the various kopfbahnhofs across Germany but we were asleep for many of them.