Thanks for the info, Sam. So it may be best to do it during the day. If we have to be awake the whole time anyway, may as well be able to look at the scenery. Probably cheaper to have a seat than a bunk, too.
Is that the route you would recommend?
We're trying to get from Venice to Paris. We will be in Venice on the 23rd, and have to be in Paris by the 27th. I was thinking with Switzerland right in the middle that it would be perfect to stop by for two or three days, but it's proving more difficult than expected to make it work.