I usually wash mine at a year, then every couple of months after that. They'll fade nicely in the next year if you wear them consistently and continue to wash periodically. You can use bleach too, although I'd do that at about 2 years. I think I throw in 2-3 cups.
What's the relationship between Coffee Shrub and Sweet Maria's? I thought the site's looked similar and sure enough when I clicked on coffee blends it shows me Sweet Maria's blends. They don't make any mention of this in the "about" section.