I pack for about 4/5 days. I found that the stuff made for runners, the "dri-fit" type fabric, is lighter and less bulky than the cotton t-shirts I used to pack. And the bonus is that you can wash them in the sink at night. I took 2 long sleeved and 2 short-sleeved ones on a 3 week trip to Colorado last year and just kept alternating between them. I have a long sleeved microfleece crew neck pullover that is my warm layer. It looks like a sweater but it is more functional (and washes and dries quickly). The most useful piece of clothing I carry is a front-zip, funnel neck, wind proof soft shell jacket that is suitable to wear on its own as a "dressy" jacket when dining out or otherwise being civilized. It has a superthin fleece layer on the inside and it is not at all bulky. This piece is my wind layer under my mesh jacket when the sun goes down, or the extra layer under my regular jacket when the temperature drops in the mountains. Easy to layer on or off and does double duty off the bike. Thin enough to layer under the riding clothes.
I carry my clothes and toiletries in a bag in one side case, and in the other one all the miscellaneous stuff: the stuff for the bike (oil, manuals, wire ties etc), rain gear, water bottle, hat, maps, small nylon backpack that folds up small to use for touring around at your destination, a lightweight travel bike cover, cable lock, multi-tool etc. The small travel purse goes there too. And, I carry my "overflow" bag - a waterproof 40 litre seal-line bag from Whitehorse Gear. It holds any purchases, sometimes laundry or shoes or extra riding gear, like the mesh jacket. When needed the bag straps on the seat behind me. I also have a top case that I keep my extra riding gloves in and that I use to store my helmet when I am off the bike. Its another emergency stowage container if I really need it.
I have over 90,000 km of mostly long distance travel on my 2003 F650 GS and I can be off that bike at the end of the day, grab the clothing bag out of the one side case, take the tank bag off and stow it in the side case, put on the cover and be done.