How Long Should Losartan Be Taken To Keep Blood Pressure Under Control?

I take Losartan 50 mg once daily. My BP for the last 2 days is around 105/60 mm Hg. This is after I have started exercising for the past 10 days. Earlier the BP would hover around 120-130 / 80-90 mm Hg with Losartan. I started taking the medicine about 5 months back. The exercise has just been started, the only change. Should I continue with the medication or reduce its dosage??