I'm pretty adamant about carrying 1 bag. First trip we didn't do that, and there were no elevators in our lodgings. So that's my rule now. 1poorlady thinks she needs more, especially if we're cruising. Carry-on in European domestic (the one time I did it) also had a reduced physical size. Bins were smaller. Limit is 22 lbs. My camera bag weighs 18 fully loaded.

I generally start at perhaps 35-40# in my medium check-in. My carry-on is Europe legal in dimensions if I un-expand it. But after a month of traveling, there will be souvenirs and gifts. At least checked limits in Europe are about 40#.

Nice thing about trains is that we don't have to worry about luggage weight at all. Plus the scenery.

I can do it with only carry-on. Did it a few times. It's not about laundry. I do sink-laundry all the time. I carry about 5 underwear, and all my clothes are mix and match (everything goes with everything else). Quick drying. But now I have pills, where I didn't before. And the longer the trip, the more I need to allow for that. For example. At least we won't have to worry about cold, which would otherwise require heavy coats.