For the time it takes. Checking the oil level at the time of each fill up is an excellent habit to get into and keep. At some point it may even save you an engine.

With many current cars if the oil light comes on it can be too late. I am somewhat negligent of this myself at times. Although I have been starting to work my way back into always checking. Other than just only before going on a long distance run.

It occurred to me one day while driving along that if an engine springs an oil leak. This is about the only way you may catch it before the oil level drops too far as it worsens.