I have had a P3Advanced for several years and learned working in the aviation industry 'If it ain't broke, don't fix it.' Thus, here is what I have been using since for--ever.
Good Luck. If you need to sideload the DJI. I have the APK. 2.8.1.
Phantom 3 Advanced Software
08 28 2016
DJI Go 2.8.1
Remote C 1.6.0
Flight Controller sn 03Z0243119
I also have the P3A, I bought it just before the P4 came out and have never updated the firmware, I too am on 1.9.x.x , not near it right now to check. But I have had no problems with it, So as Kirby says, if it ain't broke.