You need to count nights, not days.

Night 1: Rome
Night 2: Rome
Night 3: Rome
Night 4: Rome

That's 3 days in Rome, because your first day is probably shot between travel, sleepiness and jet lag.

Day 4: Check out of your hotel, get to Assisi about noon, check into hotel there (or leave bags). One-half day in Assisi.

Night 4: Assisi

Day 5: Check out of your Assisi hotel, get to Siena and check into hotel there. One-half day in Siena.

Night 5: Siena

Day 6: Check out of your Siena hotel, get to Venice (approximately 4 hours on the train) and check into hotel in Venice.

Night 6: Venice

Day 7: Venice

Night 7: Venice

Day 8: Fly out of Venice, hopefully

You're spending too much time moving between places, checking in and out of hotels. I'd eliminate Siena for sure and Assisi if you can stand it.

If you're comparing guided tours and independent travel, guided tours take care of all the transportation problems for you. When you're traveling by yourself, you have to find the right train track or the right road, correctly interpret the road signs or the stops along the train route, transport yourself from the airport to the hotel, etc.

I’m wondering what draws the OP to Assisi. Yes, Assisi is special, and we’ve spent several nights there, and maybe the OP is visiting for religious or spiritual reasons. However, if visiting for reasons of scenery or art, then I think that compared to Venice, Assisi is a bit thin. (A hotel I could recommend is the Dal Morro Gallery in Assisi - downtown Assisi not far from the station. It’s special.)

We enjoyed Assisi, but that was part of a very leisurely tour of almost four weeks. I think that if we were more pressed for time, we’d miss it.

I’d advise the OP to miss Assisi, or really think hard why he is going there, and maybe add a day to Venice. While everyone says that you lose half a day when moving places, you lose more than that when moving to Venice. Because it takes a while to get a handle on navigating around the maze of streets, and to stop getting lost.

RSF, I know how difficult it is to take the advice and/or word of total strangers.

I hope you will put your trust in our hundreds of combined years of experience. :) Please plan Siena and Assisi for another trip.

Spend four nights in Rome and three in Venice. You will BE so much happier and get to actually experience and SEE some amazing things. Otherwise, this trip will be nothing but a blur after you arrive home.

Have a wonderful time. Italy is a magical place.