I pack as light as possible in general. We typically take our "big" vacations in summer/early fall, which makes it even easier since summer clothes don't take much room. We've done three trips to Europe, two weeks each time, with just carry-on bags. I bring about 5 days worth of clothes, which all coordinate, and we do laundry a couple of times along the way. I admit that upon arrival home I'm generally really sick of the clothes I've worn for the two weeks. We try to stick to carry-on for several reasons: 1) the possibility of checked bags going missing, which has happened to us in the past; 2) we can take public transportation anywhere and don't need to get cabs; 3) we don't have to worry about hotels with only stairs and no elevators since we can carry everything up; 4) it's really nice to get off a plane and not have to wait for bags before going through customs.
It wouldn't work for everyone, and it honestly doesn't ALWAYS work for us. Last February we went to Quebec for Winter Carnival and for that 4-day trip we checked a bag, since I needed my winter boots and we needed warm scarves, hats, mittens, etc. which take up a lot of space!