I just rented a Medela pump and used it for the first time tonight. It works wonders and took no time at all compared to hand pumping!! I was just curious as to when to stop during a session. Should milk still be "squirting," "dripping," or should I do it until no milk comes out? Should I pump until I get so many ounces? Stop after so many minutes? Also, since it is more effective than hand pumping, should I still do it every 2-3 hours??