A general rule of thumb in botany (which gets complicated somewhat outside of soil) is that the plant's mass above the ground is proportional to the mass below the ground. Pots/buckets have finite space. You can only keep the solution clean and have nutrients/oxygen available to the roots. At some point there will be no more room to grow without choking out other roots. Optimizing root space? Good luck. The plants will find a way to get to where they want to be, sometimes to your detriment.