If one of them top-crops better than the other, harvest at peak fermentation to maximize that strain. If one flocculates better, than standard post-fermentation trub washing would favor it. In this case, both of those characteristics apply more to 1318 than 1056. So far as I know, all ale strains reproduce at almost exactly the same rate, but any blend of organisms is an evolving thing. As long as it makes good beer, you can continue to use it, even if the results are not exactly consistent and/or predictable.