Only in three cases you must reprogram your keyless key:
1) you change or add a key, so you must reprogram the car control unit to tell it "this is a new key, get along with it".
2) you change the control unit, so the new one must learn everything about the car, keys included.
In case 1 and 2, only Honda services can reprogram the control unit.
3) you press many times one of the key buttons when you are far away from the car, even accidentally keeping the key in your pocket or giving it to your son; in this case the key could lose the alignment with the control unit and the keyless system won't work, both front and boot doors. Restoring the alignment is very very easy, just open the car pressing one of the key buttons when you are close to the car.
Note that the key has a small red led flashing when you press one of the buttons; the led will flash also when you put your hand inside the space between the door and one of the front handle and when you press one of the boot door buttons, showing the key while transmitting.