It's unlikely anyone is going to run into any issues with repeated, unnecessary calibrations therefore.
On the contrary, repeated unnecessary calibration risks getting a bad compass calibration and that can cause you to lose your Phantom.
The kind of people that make repeated unnecessary calibrations, often don't understand what compass calibration is about and don't understand the importance of doing it somewhere away from the influence of iron and steel objects.
I calibrate every time. Even after I change batteries. The reasoning is because I have noticed when I do this every time, when I push the return to home button the Phantom will land within 1-5ft of the original takeoff spot. When I do not calibrate, it will land 5-10ft from the original takeoff spot. This is the only difference I have seen. I want it to always be precise.
That's just coincidence in your observations. More testing of that theory would come up with many flights showing the opposite result as well.
The compass (direction) and GPS (location) are completely unrelated sensors.
What you have observed is due to the random error in GPS precision.
GPS is only accurate to +/- 3 metres most of the time and sometimes even more.
Compass calibration will not improve GPS precision.
I have never heard of a bad compass calibration on a P3. They are either calibrated, or they're not. If they're not, then it would state the calibration was not successful. And because of this, a compass calibration is piece of mind. The task itself is just too easy to do to not insure the process is set to go.
Not at all. It is very possible to get a bad calibration and this forum has many examples of people doing it.
When you calibrate, it is to allow your compass to correctly tune in to the earth's normal magnetic field and ignore the influences of all the bits of metal and electric current running around your Phantom.
If you do this in an area where the earth's normal magnetic field is distorted by iron or steel objects (like on a concrete structure full of steel reinforcing or on a steel ship), you can "successfully" calibrate your Phantom's compass to work in the distorted field of that location but when you fly away from that magnetic influence, your compass is screwed up and unable to work with the earth's normal magnetic field.