[ajitkolathur]

Black money is like a weed. Demonetising currency is like deweeding. You pull weeds out from your lawn, your lawn looks good, for sometime. The weeds will grow again! If you don't want the weeds to grow, you must use weedicide at regular intervals. The idea of having expiry dates for currency is like using weedicide at regular intervals. The weeds can't grow so much as to deface your lawn.