Ladybug84..I agree 2 minimum for each chapter, but if you are offered more, then take them up on it. There is always the off chance that someone that says they are sending in a packet for your daughter doesn't actually send it.
One tip to "remind" the rec writer is to have your daughter send out a thank you note to them about 2-3 weeks after she gives them her folder. If they have forgotten to send it, this will remind them.