ORIGINAL: bassplayinDude
If I'm flying multiple packs back to back (I only have two at the moment), I wait until the first battery is cool to the touch, then stick it on the charger. Then I stick the next battery pack into my CX2. Probably takes about 10 minutes give or take for the battery to cool after full use IME.
This is exactly what I do. As soon as the drained battery is cool and ready to go on the charger, I plug it in and drop the fresh pack into the heli.