I Was Taking Valsartan 80 Mg But My Blood Pressure

I was taking valsartan 80 mg but my blood pressure has started to rise. I was prescribed 160 mg but didn't need that much to keep bp under 120/80. Now I am up to 155/95 and I am back at 160 mg but the pressure is not going down much. I see that I can take up to 320 mg. Does valsartan lose it's effectiveness over a long period of time? And will the increase to 240 mg have the desired effect of getting my bp down to where it should be?