9 cities in a month? Definitely doable, though a bit of a push. A minimum of three days/city is generally the concensus about the length of time needed to really get a feel for a place, so that would be 27 days right there, not including travel time, and some of the distances involved are fairly long. Consider night trains for the longer hauls, as they'll buy you time in country and you've gotta pay for a night's accommodation anyway. If there's any way you can extend your trip, even a couple of days would help give you a more relaxed pace. If not, figure out the places you really want to spend a lot of time, and be prepared to sacrifice a day or two from a less compelling destination so you can really savour those higher priority spots. For me personally, two days in Amsterdam and an afternoon in Zurich was plenty, but I could easily have spent a week in and around Prague. Don't feel you have to stick with a preplanned schedule - if you like a place stay longer - if you don't, leave! Even if you totally upend your plans and go off somewhere completely different, don't worry - you'll have just as great a time as if you stuck to the programme. I once dropped a planned two week circuit of France to go spur of the moment to Spain and Morocco and it was absolutely incredible. I don't regret it for a minute.