For this to be proven without a doubt one would need to run a path on old firmware and then upgrade then in the similar conditions and run a similar path and see if the times are actually different or the same.  As we know due to conditions and the way one is flying things can be dramatically different as far as flight time.

Fantasia Posted at 2018-3-31 06:50
First firmware: flightime estimate 21 mins
Lastest firmware: only 16,5 mins

Please post a screenshot from before and after ;-)

Fantasia Posted at 2018-3-31 06:50
First firmware: flightime estimate 21 mins
Lastest firmware: only 16,5 mins

Where do you see estimated 16.5 minutes?

SparksBird Posted at 2018-3-31 06:57
For this to be proven without a doubt one would need to run a path on old firmware and then upgrade then in the similar conditions and run a similar path and see if the times are actually different or the same.  As we know due to conditions and the way one is flying things can be dramatically different as far as flight time.

Not really, OP claimed that before the update DJI GO 4 displayed a flight time of 21 minutes with a full battery. Later in this thread another user demonstrated that it displayed the same flighttime before and after the update. Just read through the thread. And meanwhile quite a number of other users have confirmed that their flighttime is not reduced. I have flown one battery until warning level today and now will check how long my flight has been.

Wachtberger Posted at 2018-3-25 11:11
Here we go, you provided the convincing evidence that nothing is different after the update. This is the realistic flighttime under normal conditions (plus safe landing contingency) and nothing has changed at all with the update. Thank you very much!

Breaking news: anecdotal evidence becomes convincing evidence. You heard it here, first, folks.

djiuser_iGJqCoTNTQSa Posted at 2018-3-31 08:24
Breaking news: anecdotal evidence becomes convincing evidence. You heard it here, first, folks.

And you have done it so much better...

All your batteries are showing the same remaining flight time?