Yikes! I knew there was something I'd missed.
Now you may not have heard of the 8 day rule. Wear your pants, then turn them back to front, then inside out, then back to front again (so that's 4 days) and then swap with your tent partner - hey presto 8 days!
Now there are 5 plus myself plus our expedition doctor on this trip so in theory I could get 28 days out of one pair. So 3 pairs should see me right for the whole trip.
Only kidding ... I'll travel in a pair and leave them in KTM to pick up on my return once they have been laundered.