There's no such thing as a free lunch? Rubbish, if you're booking overnight trains in Europe you can get almost an entire half a day of free travel if you know what you're doing!
If your overnight train is leaving after 7pm then you can put in the following day's date on your rail pass and use one rather than two days of travel for the overnight trip. Simple! You'll arrive bright and early in your destination city and will have the rest of the day left to use to travel even further if you wish!
Please note This isn't always allowed and you should check when booking your place on the night train, having said that it is allowed more often than not!