How deep should my sump be?
I would not want to see 12 inches of standing water close to the slab grade in a sump pit. My first thought would be to see if you could adjust the float of the pump to turn on much sooner and keep the level down to maybe 4 to 6 inches. There should be an upper and lower level set on the pump.  it would be helpful to know the make and model of the pump so we could check the specs and see if it can be easily adjusted. Keeping water standing so close to your slab can saturate your floor and cause weeping through spider cracks. I'd prefer to see the level at or below the level of the drain tile where it enters the pit.