I dont know if there is a set limit or set number of years that you "did smoke" in the past.When I took my ploygraph it had been 4 years since I did,and yes I was honest about it.But it seems the qquestion was had I in the last year or two.Just be honest.You cant correct the things you did in the past,just be confident when you go in and take the test or answer questions.Thats the first thing that will get you fired here or eliminated from being hired,lying