Rod, the 2 year mark is a reality because fish grow and reproduce at a rate the FHM can't keep up with because they are somewhat slow compared to other species. Their reproduction rates make them ideal to jump-start a fishery-but seldom do they make it past yr 3 at most for many reasons. As your sunfish populations begin to explode, a large majority of your FHM fry fall victim to those very young sunfish and never even make it to 1/2". At some time in the 2nd yr there has to be a shift in desired forage for growing predators to make the transition and continue growing.
Lets say on any given day, a LMB has to have all it can shove in it's mouth in close proximity every day as a 6" fish.. Let's say that fish will eat 40 1-1/2"-2" FHM a day. Fast fwd to next year, that same fish has to have ample sunfish of say 2-3" in close proximity every day to maintain and grow.. those many numbers of small sunfish supporting that bass may eat literally thousands of FHM fry to support that 1 bass-for that day. Diets change as conditions change and FHM just will not provide a sustained population in those conditions even at their largest size. The more cover you have, the more recruitment you have of "everything" some of which need to be accessible for proper growth and also population control.
If you provided the habitat needed for FHM to survive I think your growth rates of everything else would suffer.