Why does a spherical conductor retain its charge for a longer time in comparison with conductors of any other shape?

Explanation

Any conductor has higher charge density at its sharp edge. Such an edge discharges faster than a spherical surface.For a spherical conductor, the distribution of charge over its surface is uniform. As it has no sharp edge, it loses its charge very slowly due to discharging action. So a spherical conductor can retain its charge for a longer time.