That is not necessarily true, as it depends on a number of things. I set my Swift 16 (a large 30 nitro sized electric heli that uses 520mm to 560mm blades) up for training a friend last summer, and using a 1500 head speed and a 4S/5000 battery pack I easily got 10 minute flights.

I fly electrics, nitros and gassers and they all have advantages and disadvantages.

One big advantage with the bigger electric, like the Century Swift 16, is that it has the same stability and maneuverability of the bigger nitro helis, but does not need one to learn how to properly tune needle valves or how to properly set throttle curves (if one does not want to spent the extra money and installation time for a governor). This makes life a lot less frustaring for them.

As for the other points you mentioned, I agree 100%.