Some of you are underestimating the true power of merino wool. I brought one light merino top on my last 5-week tour that I used on and off the bike every day. I never washed it, it never smelled, and it dried quickly. I commute to work every day using a mid-weight merino top, and I can't remember the last time I washed it.

I'd recommend that you bring just one light merino t-shirt and one mid-weight shirt as your base layers for everything. You'll only need one pair of boxers unless you ride in them. The only important item to wash is your cycling shorts, although I like to throw in my socks when washing my shorts because they're smelly synthetic material.