OK< so I'm getting about what you are. Going to have to replace the battery or get a backup. That's only enough for about 1 student's flight before it's dead. I'll fly up to 8 hours in a day!
I would suggest iFly look at offering an upgraded battery option (obviously for more money) to those pilots who fly more than 2 - 2.5 hour trips. Or perhaps the option to purchase an extra battery at checkout. Add-on sales!!