Why waste time and energy on chores such as laundry and shopping, if you can avoid it by taking a bit more stuff with you? A big roller bag is almost as effortless as a small one, as long as you are going to a semi-civilized place.
My favorite way of traveling involves a 20l backpack and a small checked bag. There is usually enough space for whatever I need, I don't have to worry about overhead space, and I don't need special travel versions of the things I use. But sometimes I take a larger (~100l) suitcase, or even both for longer trips with multiple activities.
As for trekking in the Himalayas, you should always carry clothes you don't expect to need and gear you hope you won't need. Mountains are objectively dangerous, and bad things do happen occasionally. Such as the unexpected blizzard on the eastern side of Everest last weekend.
My favorite way of traveling involves a 20l backpack and a small checked bag. There is usually enough space for whatever I need, I don't have to worry about overhead space, and I don't need special travel versions of the things I use. But sometimes I take a larger (~100l) suitcase, or even both for longer trips with multiple activities.
As for trekking in the Himalayas, you should always carry clothes you don't expect to need and gear you hope you won't need. Mountains are objectively dangerous, and bad things do happen occasionally. Such as the unexpected blizzard on the eastern side of Everest last weekend.