I try to steer away from this subject as much as possible. But since you posted the link, I do want to add that we now have much different technology now since the info in that thread was originally written. Anyone that flew either the P1 or P2's prior to the P3's know the characteristics are greatly improved.If you haven't seen this post yet, it's a great overview of the compass and calibrating:
Compass Calibration, A Complete Primer
My thoughts are that once I have a successful calibration in a known good (not magnetically influenced) area, I don't then recalibrate. Like I said earlier, I don't even remember the last time I calibrated.
It's possible to get a successful calibration in a bad (magnetically influence) area which would result in erratic flight once your P3 was launched and left the bad area. I choose to not risk that happening since I already have a known good calibration. I hope that makes some sense.
I went through 3 P2's in 4-months and 4 total by 10-months. The P3 came out and after 1 1/2yrs I still have that same P3 using the original props. It has been through a ton of beta testing for dji the 1st 6-months until I stopped working with them.