Traditionally, when meat reaches to 190F, you take it out of smoker, wrap it, and place it in the cooler for 1 to 3 hours. You indeed continue to cook the meat by the heat of meat itsself. 3 hours later the meat temp. may lower to 120F. It is nothing but you continue to cook the meat from 190F to 120F for 3 hours. It is not scientific way.
Why not just keep it at 140F for 3 hours.
You may try 120F,130F,140F,150F for 1 hour, 3 hours, 6 hours ect.
and you will find your favorite way, the right texture and taste and doness