My sister also is terrible when it comes to lies. Her actions in terms of going to her rehab sessions have been reassuring, but still so many lies about other things: big and small, from telling her bf that certain bills have been paid, to whether or not she confirmed with my mom it was OK to come home a day early for Xmas (it was news to my mom).
Unlike your husband, she had that problem before her addiction, so maybe its a symptom of her underlying mental issues. Half the time I think she really believes the things she says.
She has improved a bit with being in treatment, but its clearly going to take a long time.
I do what others above have suggested: unless its something really important, I just say "uh huh" and move on. It does no good at all to call her out on a lie.