The earth's magnetic field is in a state of turmoil at the moment. In some specific locations the magnetic variation has swung through more than 40° in just five years. Hardly a reliable means of navigation - and it is of course, a single source.
In 25 years the North Pole may quite possibly be somewhere in Antarctica. Or not, as the case may be. Its always wise to hope for the best and plan for the worst, well in advance.
