It is very simple to know if the mask is still wearable or not.
It is sufficient that after each wash or even after ironing the mask to reactivate the anti-drip finishing protection, you throw a small drop of water over the mask.
At this point you can clearly see if the mask is still protective or not. If the droplet is absorbed by the tissue of the mask, it means that it has lost its protective capacity.
At this point you can no longer use this mask. This way you avoid counting how many washes have been done and you are sure that the mask is still effective.