Each time you pour and swirl the nail polish, you should be able to dip 2-3 marble Easter eggs. After that, there won't be much polish left on the surface and it won't have a pretty marble pattern anymore. To start over with fresh polish or to swap colors, take a paper towel and run it over the surface of the water; we like to use sustainable tree-free paper towels like the Seedling Paper Towels ($5, Grove). The excess nail polish will stick to the paper towel and you'll be able to pour new polish, re-marble it, and start dipping eggs again. Repeat this process until you've marbled as many eggs as you like using different color combinations.
Related: Make Easy Shaving Cream Easter Eggs