Could be any number of years. If well protected, can be passed on from generation to generation.
Controlling blood pressure
Take a glass of water. Dip two pieces of five Mukhis in it, preferably after sun set. Drink it when you get up in the morning, before any other intake. Do not use copper glasses.
Controls Sudden Nervousness
Keep a big size 5 Mukhi Rudraksha with you. Whenever you feel nervous due to sudden shock and feel cold, just hold it tight in your right palm for ten minutes. You will regain your confidence and body will start warming up.