I've had trouble with my feet too.

A podiatrist suggested insoles (non-magnetic as far as I know) and these have been a great help to me.

My doctor suggested ibuprofen (in 600mg doses) and while this did work it had some undesirable side effects causing stomach problems so I only use this approach when it is really necessary.

With the insoles I seem to be getting little or no pain from more than two dance sessions a week.

I think Tetley (and Martin) are right that it is necessary to maintain a basic level of fitness by exercising well even on non-dancing days so that you come to the dance sessions in the best condition to enjoy yourself without the worry of pain and injury.