As Woodie says, there are many variables. I'm flying the intermediate class with a light plane, the Shinden, with the Himax motor and a 20.5 x 14 prop. I'm using about 2800 mah per flight. I start my timer after I taxi out to the centerline and get lined up. I usually finish my sequence at the 6 minute mark and do the standard turn around and land at about 6:20.

I bought a 5000 pack thinking I could practice a little longer but the weight difference made the plane handle differently so I don't recommend that.

So, the bottom line, I would suggest the 4400 mah packs.