Since December, 2016, our family of three has been traveling full time with <7kg carry ons each. In cold places, e.g., Tibet in January, Beijing in February, NZ in early October, we buy cheap warm clothes at thrift shops or discount stores, then give them away or leave them at the airport before leaving. Just in case the airline asks to weigh our bags, we usually wear warm winter clothes, hats, coats, gloves, etc, on our bodies when checking in for flights. After we get to the gate, we can rearrange our stuff, packing some of it into our bags and keeping some stuff out to use as pillows and blankets on the plane. Mostly we've been staying in Airbnb apartments with washing machines, so we just wash small loads of laundry every other day, or so. In places where we don't have a washer, we usually wash our underwear, socks, t-shirts, etc, by hand when we take a shower, and then hang them up to dry every evening. My wife and daughter have a little more, but I've only got two pairs of underwear and two pairs of socks, so by the second day, at the latest, I've got to wash clothes.