My late father-in-law was big on waiting until nothing, and I mean nothing, was coming out the drain plug.
Wife tells a funny story about the first time she took her car to an oil change place after she moved out and was living on her own.
She took a book to read because in her mind it took two hours to change the oil, she never knew any different.
She goes into the waiting room, gets about three pages into the book, and they tell her that her car is done.
"Huh? What?" How can that be?"