In my opinion it's different for each person, and seems to be the more mucus one has, the more you spit.
I don't spit much at all, just spit out the oil then maybe one more time. My mom and husband spit more. My mother had a tumor in her throat (that is almost gone now, doctor was amazed) and they wanted to do surgery on her sinus cavity, so she has tons of mucus and spits for several hours afterwards. My husband has allergies and spits for about one hour.