The key is effective energy management, shock cooling an engine will not pose a risk if you plan ahead with effective energy management. If i remember rightly in most Colombia aircraft the POH reccomends that you retard the throttle at no more then 2"MP per minute to prevent shock cooling. that to me seems like a long time to retard your throttle from the curise setting to a decent setting. The trick is to simply plan ahead and be smooth with your throttle
adjusting your mixture to suit your decent will also help to keep the engine nice and warm. You probably already know that with engines fitted with an MP gauge you really want to keep the MP in the green band at all times unless on finals to keep things warm