WhoHe said:

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As others have alluded to … it appears you're only using Venice and Rome as arrival/departure points and not part of your trip. If that's the case, and you only have a week or so, fly in and out of Florence or Milan.

Cut Sorrento out, and replace it with a few days in the Cinque Terra instead - personally, I prefer staying in Vernazza or Corniglia. While in Tuscany, I wouldn't go further south than Sienna (which is a wonderful place to visit itself).

This would keep you more regionalized and thereby replace a lot of travel time with exploring time, and cut out two pain in the ass cities that you already aren't planning to spend any usable time in.

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