overall goal is zero runoff. runoff leaches out nutrients and microbes. just be careful and use good judgement. i was helping a friend get into organics and told him the same thing... no runoff. well he let his soil get too dry and it became hydrophobic. then when he would water it would go right through the pot and he would stop watering because of, you know... the runoff lol. well several weeks of this went by and i stopped over to check in and saw a dwarfed stressed plant and I was like WTF why didn't you say something. soil was so dry i cant even believe the plant was still living. after i set him straight, the plant recovered and he had a successful grow.