Hi
Apart from the minimum of six needed to fly a heli. More Channels can come in handy if you say, fly scale heli's. An airworlf for instance you would need another channel if you want to use retracts, another on if you want add landing lights that can be switched on and off during flight etc.
You MIGHT go over to Nitro Heli's one day, then two additional channels come in handy if you want to use a governor and mixture control for instance.
Believe me, you can never have to many channels
