Flight time (battery)
Flight time on a single charge ranges from 5 minutes to around 30. Manufacturer estimates are always on the generous side, so expect less in real-world flying conditions. You also need to allow time for the drone to return to you to change batteries, so effective flying time is shorter still.
If your drone is for professional use, don't skimp here. When you consider that it can take more than two hours to charge a battery, you'll want to have a few spare batteries in your pack. If you can afford it, always go for the larger battery.