Battery run time depends on the type of flying you are doing. You should get upwards of about 7-8 mins hovering on a 2100 pack. Get a couple of extra packs that way you can be charging while flying. You will get more battery time once you get into forward flight because the blades are more efficient (transitional lift) and the motor does not have to work as hard to maintain flight.

The biggest and most important lesson when it comes to helis is to have an experienced pilot help you setup the chopper and to help you through your first initial hops. DO NOT OMIT THIS STEP. You will pretty much guarantee failure if you do not heed this warning. There are very few pilots who have managed to figure it out on their own. Find an experienced pilot to help no matter how far you have to drive.

Good luck!