A lot longer than you think! When I quit (last October), I noticed when I was pulling out my winter sweaters and coats, that they still stunk from the previous winter! Ended up having everything dry cleaned.
Get the heck away from cigarettes and smokers! It's a dangerous and filthy habit that you cannot hide! The smell stays in your hair and clothing until washed, yellows your teeth and fingers and blackens your lungs. Every adult smoker regrets starting!