So I will be sending my subscribers good valuable contents through emails. In between, I will send some promotion emails to promote some affiliate products. I often heard people say that people don't buy something until they've seen it for 5 or 6 times. So is it important to repeat telling them about one product for like 4 or 5 times? How do I do that? Do I send out one round of all the promotion emails about different products, then send out those promotion emails again in round 2 and then round 3? How many times in good for repeating promoting a product and what's the right way to do that?