I’m often as by individuals how long a referral marketing campaign should run. The answer is this: First, you need to be patient.
Sending one referral marketing campaign to someone is not going to do the trick. Most people are not sitting around just waiting to receive some interesting information and then are going to suddenly start sending you a lot of business.
The second answer is this; Once it does work, continue sending it as long as it yields a positive return on investment. Think of your referral marketing as going to the bank. If you send it out and over the short or long haul it yields a positive return on investment, KEEP doing it.
I have seen people create a referral marketing campaign that is enormously successful, and then stop using it. No, keep using it until it quits working.