Our drones can fly for up to 27 minutes on one set of batteries.  We carry a total of 16 batteries, often more.  We can re-charge batteries four at a time and fully re-charge in about 45 minutes, allowing us to provide as much flying and film as you need throughout the day, normally without interruption.  It takes about 60 seconds to land, change a battery and get airborne again.  We have a small petrol generator specific for LiPo battery charging for use in remote places, power sockets in our van, or we use power provided on-set – so can be pretty self-sufficient most of the day.