In that case your list is going to be up and available for long time because mixers are not going anywhere. If the situation becomes completely untenable for mixers because of a concerted international effort by law enforcement agencies to ban them, then you will have to make the decision. You never know, in the future maybe mixers will end up being licenced on a country to country basis.
At least in the case of BitMixList, if it comes to the point where mixers are completely outlawed worldwide, I can just take the site down.