Is Medication Necessary When Having BP Of 140/90?

I m 46 yrs female.taking nebistar 5mg one tab daily morning 6am & Benitec-A at 8am and Rosutec 5mg. at night my BP was 140/90 but after taking these medicine now bp is 120/80 .my weight is 66kgs,height 5 3 .i m not diabetic.my family tradition every body had BP avg- 140 / 90 . My question is for how long i have to keep taking medicine for BP or is it really necessary with these medicines.