I've got a few Shureido NW3 and I've washed them all different ways. I always wash them in the machine, but the temp of the water various. I've done it from cold, to the hottest setting. And one of mine is still going (has been patched up a few times) after 5 years.
and I generally chuck mine in the dryer too, even though it says not too.
Hope this helps!
The traditional Karate guy, from an nontraditional background