Birds in flight are perfect to practice indeed. I regularly go to the canal here to shoot gulls.
When I shot burst with the D3300 my buffer was in constant overload and more often than not I had to wait on the data transfer. When shooting the D750 I have a second card grabbing that overload increasing my continuous. Of the close to 4k shots I took with it, I don't think 2 have been on that second card.
It's not because the D750's buffer is so amazing compared to the D3300. It's because by now I learned when it no longer pays to push the button. In the beginning you suffer tunnel vision and don't notice in many of those continuous shots the subject got too far out of reach and even when cropping it to death, there's little left. Or you're shooting animal butts. You have a whole lot of action shots and it is a whole lot of data costing a whole lot of time to upload and check. And a whole lot ends up in the trash bin.
The moment you are aware that what you see will either be a little dark spot in a whole lot of shot or clearly visible and filling the empty space enough, your buffer increases exponentially.
