It appears that you truly love your other half. Since you have once before spoke with them about this addiction there should be no more lying or denying about it, unless they are ashamed but, even with that there is no justification to continue lying about it when asked. Allow me to offer you this, take a bit of advice a very special person gave to me recently. Sit them down and talk about it. Since you have done this at least once before it cannot hurt to do it again. Do it as many times as you need to IF you really love and want to be with them. Explain to them that you have known about their addiction for some time and you are aware almost every time you see them in this condition or the after affects of it. Tell them how it makes you feel when they outright lie in your face. Let them know that is not the addiction they have that hurts you most but their lying to you about it. Now on the other hand there could be more going on other than the addiction you speak of. This, most likely is something they absolutely don't want you knowing about. Be careful in the fulfillment of someone's fantasies when you know they will lie in your face, it just may backfire and you could end up the odd person out.