jecasc - 7:24 am on Jul 8, 2011 (gmt 0)
It depends what you are selling. I sell non-durable goods which are used up in about 3-6 month so I have customers who have been ordering for 10 years and have placed 30 or 40 orders in that time. About 60% of my daily sales are from returning customers. However I do not "rely" on my customer base. I always try to bring in new customers.
However if you sell "buy once in a lifetime" products things will look very different.