I kinda wagely remember some lawyer saying that sending response too early could also cause delay. What he said was that once the INS sends RFE the file is sent back to the store. The receiving office tries to retrieve the file from store when they receive the response to RFE, attach it to the file and sends back to the requesting officer. If the response is sent too early, the receiving office does not find the file in store and put aside the reponse for a period of time causing delays. According to this source, one should not send the response before 10 days of issue of RFE.
I don't know how true is this.