Sanyo 720mah nimh question...

I have a sanyo 7 cell 720mah nimh battery. How long should I be able to fly for? Currently I only get maybe 3 mins on the sanyo pack, but on my powerex 8 cell pack I get about 10 mins.

7 nimh's won't deliver a high enough voltage at the load
we need, 7- nicads are fine though. Incidently, I have
played with 7 nimh using the orion elite motor with some
success- 10 mins using 7 cells as opposed to 12mins with
8 cells. ( Fixed pitch, hornet CF blades 9 tooth pinion in
a std piccolo )

I wasn't very happy with the Sanyo 720mah nimh pack with the stock motor, but after installing the
Orion motor, I'm quite happy with them. I get around 8 minutes of flight and then a couple of minutes
of ground effect scooting or hovering.