This is interesting. Until very recently, the only wool base layers I had were three Sugoi Wallaroo tops. And I always wash them after wearing them once. Sometimes I wear them for bike rides, but sometimes I wear them under sweaters for everyday.

However after reading this thread, I think I will start to air them out and wear them more before washing them.

I have a top-load washer. I usually put the wool stuff and other more delicate things at the top, because I think I read somewhere that there is less agitation at the top.

BTW, I have a friend who highly recommends Wabi Woolen jerseys. Their fabric care instructions are here.

http://www.wabiwoolens.com/jersey-care

It begins thusly:

"Washing is hard on wool. There is no way around that. So the best way to care for your Wabi Woolens jersey is simply not to wash it. But let’s face it, that only works for so long before your riding partners and significant other start to make funny faces when you put it on. Eventually, you have to clean it and here’s the best way to do it, step-by-step:

*REMEMBER*

Agitation is what shrinks wool. The more gentle you are with your jersey when it is wet, the less it will shrink.

Washing

1. Wash before wearing and always follow these instructions. When you think it may be time for another wash, wear it a few more times, just so you’re sure."