I don't think it would be a full 12 years, and even if the price was a loss in accuracy or range the ability to fire after the dominant muscles tired might be useful.
Amy, optometrists seem to think of mixed dominance in terms of near and far, but the far test is individual letters (geometric form) and the near test is a reading card (language). I can read simple music at singing speed (okay, I'm rusty) but only if I force a switch to my right eye and process it with the high-speed language part of my brain.
These fault lines are sharper in southpaws than in dexters, but southpaws have faster average reaction times, according to both MLB and the US Air Force. Back when it was the Army Air Force, they tested Babe Ruth and found that he had the fastest reactions they had yet tested.