Making the world better, one answer at a time. a superbug is a micro-organism that is resistant to most anti-biotics. the superbugs in recent history are imune to all anti-biotics,except one.
Both electronic and paper versions of Series I savings bonds are purchased at face value and earn interest until they are redeemed or reach maturity. You must hold Series I bonds for at least 12 months before redeeming them. Series I savings bonds will continue to earn interest for up to 30 years. They will cease paying interest once they have matured.
The current rate is 3% so 72/3 means it will take about 24 years to double or reach face value. The interest paid in the past was variable (I have those bonds). All EE savings bonds be it paper or non-paper will earn interest for 30 years. Therefore, you must cash your bonds at 30 years.