I worked as a manicurist/pedicurist for about 3 years, so I know about calluses and fungus...
If you use a pumice stone or any callus remover on your feet every day that is WAY too much. The callus is there to protect your bones from pressure and if you constantly take off the tough skin and expose the new soft stuff the patches will come back with vengance every time. Moisturization is the only way to keep them away.
Also, the calluses can get worse with age. Poor circulation or diabetes can eventually lead to alot of keratinized skin...this hard, built up, compact skin that does not slough itself off.
I have been oil pulling for 2 months now and have noticed that while my skin is softer, rubbing the OO (Olive-Oil) or sunflower oil right in helps the best with my dry skin. I used the same oil on customers for soft feet. Rub oil on your skin and then cover your feet, hands, whatever with hot steamy towels!