I wash my clothes every time I wear them, which sucks because it's hard on the clothes and camo is expensive. But I don't want to cut any corners. Usually I'll wash them in scent free soap on a short cycle in cold water and then hang them out on the line to dry. Once they're dry, I'll bag 'em up.
Also, it's not just sweat you have to worry about. We shed millions of skin cells a minute and deer can smell those cells collected on our hunting clothes. Just to be safe, I wash them every time.