I always do initial tests for new firmware releases - for all my aircrafts - from the same place and - if possible - at the same (or almost the same) time.
The main reason is that I want to evaluate each build using the same - as much as possible - environmental parameters.
The first thing to test is how much electromagnetic interference the aircraft can handle by flying inside a highly congested area (a WiFi "bubble") while testing overall stability/performance (i.e FPV lag) and critical functions (i.e RTH).
If everthing goes well, I go to the next step: testing the aircraft at the local
R/C airfield test location which is a torture test for the stability (especially for the camera/gimbal), as this area has 80% of the time winds over 3-4 Beaufort (even more when flying near the shore).
This is the next step in testing Build 822 which I hope to do this weekend.