Sorry ... I think I'm retarded a little or my english skills aren't good at all ...
Regarding the 50-100 mile I personally think it can be easily pushed towards 200-300 miles (400-500km) without any big/visible difference in the calibration. I've flown my good old P2V at 650km distance with no compas calibration and it was perfect.
You are probably right. I am basing this on the early days of the NAZA when flyaways were a little more common than these days.
Both my Phantom 1.5 and my XuGong v2 (Naza v2 FC) fly off a calibration that i did maybe 2 years ago and are both locked in. I have flown them both all over the UK with no issues inc 400 miles away in Scotland. I would have normally calibrated it again at the time but i flew it with no probs without even thinking about it and then just left it be.
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