MacBook :: Maximizing Long Term Battery Life?

I have a MacBook and my strategy is to keep it plugged in as much as possible to avoid using charge cycles. If I use it down to 50%, then get home, I'll plug it in so I've only used half a cycle. Then when I'm just using it around the house, I try to keep it plugged in.

My friend has a completely different strategy. At the Apple Store, one of the salesmen told him that he should use it down to almost nothing and then charge it back up again. He would never plug it in at 50%, but wait until it is 10% or less. He gave me this analogy: if you have a bottle of milk in the refrigerator and you have a cow outside, you refill the bottle when it is empty. If you keep refilling the bottle when it is only half empty, that milk is going to go bad. He really doesn't understand how it works himself, but said something about the battery's memory? I never imagined that a battery would have its own little memory or something, but now that he mentioned it, it does seem reasonable.