My guy cannot maintain an erection without viagra. He drinks a lot and smokes a lot of weed. He has had this problem long before I knew him and I am guessing it is because of his lifestyle. My question is, is he going to become desensitized to the drug and no longer be able to maintain an erection in the near future? Will the effects of viagra or other similar drugs no longer be effective for him if he continues on using it in the manner that he must to maintain our sex life?