Up until now there has always been a problem with buying multiple backup batteries for your Apple laptop and the fact that you would have to pull and replace each battery to charge it. Which in some cases could require waking up in the wee hours of the morning to do the switch.
Now there is a solution from NewerTech, a Mac-Book and MacBookPro battery charger. The charger is capable of charging two batteries at once, even your higher capacity aftermarket batteries, but it unfortunately can only condition one at a time.
The NewerTech battery charger will run ya about $150. It may seem steep, but for the ability to charge multiple batteries, it's a steal.