People will caution about the stain, but most of the pipes I've cleaned, the stain has been pretty well "set".
I agree. I think there have been maybe 3 that have showed a readiness to lose the stain. One was a new mid range priced Mastro de Paja I purchased several years ago. Now I test them to see if it is going to be problematic, but out of close to a hundred estates so far it just has not happened.