So, just try it.
Everybody recomends after a firmware upgrade to do a new IMU calibrations, Gimbal calibration and compass calibration.
I personaly do a cold calibration by placing my phantom directly on Air condition to get cool. I leave it at least 30 minutes, because after a firmware upgrade the phantom is really hot. After that, with the remote on and the app on the calibration menu, ready to go, i power my phantom and as soon as i get the IMU calibration button ready, i start the process. I do this very fast to prevent the IMU to get warm up by the phantom.
Calibrate in a iron free ambient. In a wood table for exemple and must be level
The advantages of this is you will get faster warm up times when you start the phantom and i personaly think that the phantom will be better calibrated in their sensors.
just do it one time and see if that drift problem will go away, because drift cam be caused by bad calibrated IMU.
You can also put it in the freezer, but i dont advise that. if you do, make sure you put it in a plastik bag to prevento moisture from the fridge to get into the phantom.