A couple of years ago I was on a train from Florence to Rome. A woman with a HUGE suitcase that she obviously couldn't handle entered, and asked if I could hoist it into the storage bin for her. I had a rotator cuff repair on my shoulder six months before. Out of a sense of chivalry I didn't say no, and unsuccessfully attempted to lift it, and re-injured my shoulder. I would suggest as a rule that you don't bring luggage that you can't handle (or hire someone to handle it).

I've stayed in Italy for as long as three months with just a carry on. In fact, I've been here for two months now, and came with just a carry on. I bring some old things that I'm willing to discard, and buy a few new things now and then. When I get into the shower the underwear goes into the sink with some detergent. When I get out of the shower the underwear is rinsed and ready to be hung to dry in the shower. I do the same thing with most clothing, and just send a few things out, like dress clothing.

I haven't checked a bag since a trip to Lago di Como was ruined by lost luggage about ten years ago. In my opinion it is worth it to just make do, and not worry about luggage. Large portions of Italy have a problem with mosquitos, but I've never had an insect problem in a hotel or residence.