20 minute flying time is pretty bad - kind of delegates this to a "We want this picture" or "We need this shot" type of thing, not "Turn it on follow mode and let's see what we get after our walk/game/session" which would be a lot more useful
That's what the current energy density of lithium polymer batteries roughly is on a drone with this size props and weight. Not much that can be done aside from hoping for better battery tech!
