Hey Pooks, my DH and I both have several of those thin merino layering tops that we use not only for cycling but also as a base layer in cold weather just everyday. I often wear the SW crew long sleeve underneath their Zip-T and it's so toasty and nice feeling.
It amazing how I don't get any underarm odors at all wearing merino several times! I only wash mine after maybe 4 wearings, and like you, only because it will take on my deoderant odor, not because it smells "bad". (maybe I should use less deoderant now!) I actually wind up doing far fewer laundry loads since wearing merino base layers.
We save up quite a few merino/wool tops and socks and longjohns, and then do a small machine wash of them on GENTLE with Woolite and cold water. I fluff them a little bit in the dryer on LOW for only about 15 minutes (gets the cat hairs off for one thing!), then I just lay them or hang them out to dry.
Woolite is easier on the wool fibers than a harsh detergent like Tide. We tried Ivory Snow liquid, which was recommended by the Woolistic brand merino manufacturers, but we hated the smell of that stuff and went back to Woolite.
If I take good care of my real wool stuff I hope it will last almost forever. (it sure ain't cheap!)