When I would take a shower, the socks and underwear would be placed around the drain. This caused them to become immersed in the suds, thus re-purposing every shower I took. I would scrub on them some to get them clean, wring them out after rinsing in the shower, and then hang them to dry.
For approximately 165 days now, I have alternated the two pair of socks and underwear each. The merino wool does not hold odor, dries somewhat fast, and has proven to be sturdy compared to my cotton socks. If you break down that each pair has been worn roughly 80 times, the quality shines through. There are no holes or rips in either socks or underwear. The socks are possibly thinning some, but were not very thick to begin with. My guess is that this would be roughly two years worth of wear compared to the "usual" sock and underwear drawer collection.
There are a few things to point out. Drying clothes on the line probably makes them last much longer, and I do like not having to fold a bunch of socks after doing laundry. I would, however, recommend having a third set. if you take two showers in one day, the first set may not yet be dry. I am not positive how much water would be saved, if any. I did not make a diligent effort to try and save water, I enjoy a hot shower in this frigid climate.
It is something to consider when purchasing items, what is quality, how can I make it last, and how much space does it fill. I really could more than get by with four sets of each, and take up very little space. I did also try this with workout type shirts as undershirts. It worked well, as they dry fast. They were just not made as well, and started to unravel with constant wear. The houses built in the early 1900's have very small closets, and we now have them so large, they are literally the size of some apartments in large cities. This was a fun experiment, which is now a way of life for myself. It is simple.