We will be arriving and leaving Rome by car. We will be staying 3 nights at a location strategically between Vatican & Colosseum.
Should I close out rental & get another? Original rental is from Rome airport & "second" drop-off would be Florence before train to Venice.
Vatican and Colosseum are at the opposite ends of Rome’s rather large city center, so a location strategically located between the two could really be anywhere.
Whether you want to return the car and start a new rental later or keep it in a garage is a decision that depends on cost and convenience. Parking will likely cost you about €25-€30 a day. If returning and picking up again with two separate rentals costs you more that the cost of parking for 3 days, then you might as well park the car. Renting a car for 3 + 3 days may cost you more than renting for 9 straight days. So play with the various scenarios and see. Also consider that if you plan to return the car at the airport then the taxi from there is not cheap as Fiumicino (or Ciampino) airports aren’t too close to the city center.