Winter storage: battery charging

From what I have read, I know that my motorcycle's battery needs to be charged once every two weeks or so. However, this is not the case. 

The first time that I hooked the battery up to the charger was three weeks after I removed it from the motorcycle. Even so, the battery had been fully charged in only five minutes. Surprised, I decided to keep track of its voltage and see at what rate it drops with time. Well, I do not know if it is because of storage conditions, or because the battery is almost brand new, but it hasn't really lost any potential during the last three weeks. The charger cuts off at 13V and my indication today is 12.68V, so good thing to know there: if your battery is new and you keep it at room temperature, you will most likely not need to recharge it often at all. I wonder if it will drop under 12V even after two months without charging.