I can't for the life of me find a recommended check-in time for our night train from Munich to Rome, which leaves Munich at 9pm. Would being there an hour early suffice, or would 90 minutes be advisable? (We are a family of 4, comfort flexi 1st class.) Thanks!
If this is a regular night train (not the Orient Express or something), my experience was that there isn't really a check-in like at an airport. Ninety minutes before departure in a busy station the your train might not even be there. If you have reservations, just show up at the station maybe twenty minutes before departure, locate which platform your train is at on the big departures board, follow that platform (Gleis) to your carriage, show your tickets to the conductor and get aboard. Since you'll be crossing a border overnight, the conductor will need your passports, and will show you how to use the light and heat systems in your compartment. A lot less rushed and stressful than air travel!
For sleeper trains in Europe, you don't need to check in before departure. The conductor on the train will deal with the formalities. But I would suggest arriving at least 15 mins before departure so you find the right carriage. Night trains can be very long and often divide en route, so it's good to find where you are supposed to be before hand.
Bon voyage!