I have two packs and just came back from our seaplane pattern competition where I shared my Eclipse with a fellow modeller, 6 flights in 2 days no problem at all. Charging time for my 10S3P Kokam with 6000 mAh (using about 2500 mAh per flight (approx 8 min.)) was less than 1 hour, packs charged during the day or in the evening and always ready. Ok it might not be enough if training is intensive, but more than enough to fly and have fun.

Two is minimum, four is ok, six or more is definitely "upper-class", but not needed for most of us.

@Chad : good job at the WC - hope you had a lot of fun!

Regards,
-Fabrizio