When we do multi-day trips, often expedition canoeing rather than paddling, but as the portaging involved still means going light its probably still relevant, I carry about 3-4 pairs of underwear for a week. Two base layer tops, one bottoms. Thinnish fleece jumper, softshell, softshell trousers, plus waterproofs. 3 pairs each of inner and outer socks.
We tend to do a couple of hard days followed by a short day (or even a day off occasionally). On the short days, I sometimes, but by no means always, do a little simple laundry in a stream with Lifesystems eco type "do anything" soap stuff. Which may have minimal environmental impact but also has minimal impact on soiling in these conditions. I just wash undies, socks and base layer top. Hardest thing is getting them dry, so if its wet for days, I probably won't wash them at all. Tied to canoe/pack gets the worst off, but its normal to choose the damp but clean set in the morning and dry them on the body. I always keep one set, especially socks, absolutely dry and protected in dry bags, for those occasions when you NEED to get warm and dry quickly at the end of a rough day. Next morning, these go back in the dry bag and the damp stuff goes back on.
I'm happy to pull on pretty grim clothing when I'm in the wilds, but I do make sure I wash myself regularly, even if the water is bloody cold! Feeling clean underneath is more important than the clothing I think.
By the end of a week or so, I'm sure my clothing reeks. By the end of the second week, I don't give a hoot.
I do remember queuing in Mallaig Co-op after coming straight off the water after a tough sweaty paddle at the end of a week out, and turning to notice a remarkably attractive young lady just behind me in the queue. As I turned my head, my nose neared my base layer underarms, which was somewhat of a shock to the olfactory senses. Needless to say, she kept her distance. It also made me realise what I'd put the kind driver through, who stopped when I hitch hiked back to get the car at the end of the trip.
