Dependant on what clay ( make , type ) you are using, but in general, Chavant J525, CM 50, I307 Y2 etc. if the average warming ( Usable temp ) is 150f or 60c then around 20 mins then it gets a bit to hard to drag large templates.
Most of you final detail work, finishing etc will be done when the clay is back to room temp say 75f 23c We usually drop our studio down to 70f 20c when we do our final finish.
As to length of working time after a model is finished, ( Rework, modify, change ) I have seen 20year old models bought back to life very quickly
sorry, i couldn't understand. If the clay gets harder at room temp than why do you drop down the studio temp to 20c instead of rising it so that you can work on it easily
