That sounds about right to me. But it's been a while - now I use a proper charger!
The problem with the e-sky chargers is that they only output 800mA if I remember and the battery is more than that (1000-1200mAh ish?). This means that it's being charged at less than "1C". A battery of any capacity charged at 1C will normally take less than 2 hours to reach peak voltage. (1C is the rating of the battery in mAh. so if you charge a 1200mAh pack at 1C your charger would need to output 1200mA.)
Just ensure you do not charge the battery immediately after flying - leave it half an hour or so or it will be dead in no time.
However, 7 mins is pretty good on a standard pack. I get appx 9-12 on a 2200Mah pack buzzing about - and thats double yours!
My 2200 Mah pack used to take 4 1/2 hours on an Esky charger! Normally they say 2 hours maximum as this would indicate a problem with a cell not reaching peak voltage. But if your charger output is less than the battery mAh rating then 2 hours or thereabouts is about right.
Hence why I have gone back to flying Nitro
Fuel n go