So you pour some oil in that floats on top of the water acid mix. How much time could it be in contact with the Oxygen and Hydrogen as it bubbles off in an overcharge? It does not seem like you'd be able to recombine those into water effectively.
I suspect there would not be much difference and although it's patented someone would be using it if it was cost effective. Three times longer means a 15 year battery. That's not happening.