Dienogest 2 mg. Much regrow per month?

I was diagnosed bilateral ovarian emdometriomas. As I'm unmarried & there is no possibility of marriage for another 2 years. After 2-3 years I may be willing to marrige, so my doctor prescribed me Emersa 2 mg once daily. I am taking this medicine for 19 months & also continue it & each 3 months usg report says there is an reduction of cyst. Before treatment at the time of period I have a lot of pain. But during treatment I have no pain, I'm fine also, lead a happy life but some times got depressed when I though about my future fertility & negative thinking also. But most of the time I spend a quality of time. As I'm well by using this medicine. MY QUESTION IS THAT MAXIMUM HOW MANY DAYS SHOULD  I TAKE THIS TABLET WITH LESS SIDE EFFECT? If I off this tablet, cyst may regrow & how much regrow per month? [Last usg report: RO cyst size 1.7*1.3 cm & LO cyst size 3.0*2.7 cm, POD is Clear]