This is a recurring question that a lot of people tend to have. To help maintain the luster of your countertops, just a dash of mineral oil helps a lot. This can be applied weekly.
The mineral oil helps in keeping the epoxy resin bright and shiny on the surface. It would help if you also remembered that excess mineral oil could make the surface cloudy and dull.
The excess oils can always be wiped off using a clean cloth. Epoxy surfaces also tend to stain easily, so it is advisable to keep the specific features of the epoxy resins you are using into account.