If I hear you right, you are asking how thick/thin the pad can be before it/they need replacing ?
I would say 3mm of material on it and they need to be replaced, they are about 7/8mm material when new.
I sympathise with you and have seen this myself, with men just ignoring or treating ladies indifferently just due to gender, please accept my apologies for all the ignorant men out there.
If I am not understanding you correctly, please feel free to PM me and I will do my utmost to help you resolve this issue.
tabetha