When making a big change in your life, they say to allow 1 month for ever\y year that you were involved in the activity that is no longer part of your life. For instance, if you were at a job 10 years, you'd need to allow 10 months for that period of your life to be behind you so that it no longer has any bearing on your current life. So after 31 years of being "in" it may take you a little over 2.5 years to get over it.
Most people view the JW religion as being fanatical or cult-like. If you are having obsessive thoughts about JW's it's because you/we were systematically "indoctrinated" or "inculcated" as they like to call it.
As with all obsessive thoughts, you'll need to train yourself to get them under control. It might be a good idea to set aside a time each day where you allow yourself to think about JW related matters. Each time you have an unwanted JW argument in your head during the day, you can remind yourself that you're only allowed to think about those things during your designated time of day. Later, at that designated time, jot the topic down in a notebook and include your counter argument and then put it aside. That way these thoughts will have had a conclusion, rather than circling around in your mind, further ingraining them into your subconscious. Close the note book and say out loud or to yourself, " I have control of my thoughts and I decide what I'm going to think about". You can also make this (or something similar) a "Mantra" that you use during the day when you catch yourself thinking unwanted thoughts.
Eventually this healthy habit will replace the unhealthy one you've fallen into. that of obsessively thinking of all things JW. as they randomly enter your head. Eventually you'll be able to dismiss these and other unwanted thoughts from you mind as they arise.