One puzzling observation is that you can add too much solvent. The following applet should clarify this for you. Move the scrollbar and note that the yield goes through a maximum. You probably would not benefit from trying to reach this maximum exactly because the cost of so much solvent is an important consideration.
A little reflection leads to understanding. Note that the amount of total solvent is increasing. Even though the solubility decreases, the amount of substance in solution is the solubility times the volume. Too great a volume allows too much to remain in solution. Also, it takes an infinite volume of solvent to approach 100 % solvent.