We're all different so take your replies with a grain of salt. I'm working on an itinerary for the South of France and Northern Italy next September/October. By then I'll be 72 and my wife 70, so we're slowing down a little bit, but both of us are in excellent health and capable of walking several miles. So we've done the Europe trip before staying in several places for two to three days each. But it seems like you spend half your time packing, unpacking, and taking trains between cities when you really haven't taken the time to see everything or relax a little bit. So now I look to book hotels for mostly 4 days in each location. For example next Fall we'll have 19 days in Italy, so only in Cinque Terre will we stay for 3 nights, but Milan, Florence, Venice, and Lake Como (Bellagio) will be four nights each. I really wanted to spend time in the Dolomites too, but decided it would have to be another trip since the travel times in the mountains are sometimes much longer and we didn't want to spend all day on a train (7 hrs Bellagio to Bolzano). So my only suggestion is you might want to consider cutting out a location and spending more time in one or more locations. For example you have two nights in Varenna, which really gives you one day of sightseeing before you're packing up for Vernazza and a 6 to 7 hour train journey. And across the lake from Varenna are Menaggio and Bellagio, both very cute towns with lots of things to do. From there you can also take a side trip to Lugano in Switzerland or the town of Como.
These are all trade-offs and tough decisions. I can't tell you what the best plan is for you, but know that whatever you decide you'll have a great time and wish for more. Good luck!
