I am not really an expert about using SNAs efficiently, almost every time I use them I would have scored the suite upgrade even without so it felt like a waste. JWM has so many suites that I would say your odds of a suite upgrade without using SNAs in normal conditions are good. However hotels in Dubai expect high occupancy due to Expo Dubai, whether it happens or not remains to be seen but if occupancy ends up being high then indeed perhaps you should burn those SNAs to improve your odds. It also depends where else you could use them, if they will expire soon and you have no better inspiring destinations where to use them, then it could be a decent choice.