Mag readings are showing various responses under no change

Would this "slower startup" cause eventually cause issues if you called Puck.mag() too quickly?

Not really - it just means slightly higher power usage.

Im fairly fresh to messing with this so far but didnt know if it would be more power efficient to leave the magnometer on for an extended period or just get single calls over a quick interval.

It's definitely more power efficient to just leave the magnetometer on and respond to Puck.on('mag' events when they happen - that way the Puck is able to be asleep most of the time and to only respond when it knows there's a new reading.

You can supply an argument to Puck.magOn() to say how often you'd like to get readings.

But either way Puck.mag() should have worked reliably regardless of how it was called, so it's good to get that fixed :)