I have taken oratane for 2 months and my face is about 75% better. if my doctor decides to stop me using it. how long the results will last?

Varies widely: I usually put a patient on Isotretinoin for 5 months. The 'cure' rate is supposed to be about 70%. Some people will never breakout again. Some may have minor acne breakouts. Some have to use a second course of Isotretinoin if other products don't work. Acne could come back any time from one month to years after stopping isotretinoin.