Even though the amount of bussines with your company as supplier seems low you did in my opinion an effort from your part to help your customer.
Yau may have had a different perspective regarding the benefits of the visit, and that is understandable. Still a good relationship and mutual respect encourages comunication, which is of benefit at the end.
If I remember well, the tragedy of the Challenger traced back to a single defective and inexpensive gasket. We all would had wanted this issue prevented, so don't feel the visit was waste of time, and let your customer learn from the experience and from you. It can take a while for them to learn but we all make mistakes from which we can improve.
Now, if your customer is on the medical device sector you never know if one of those visits to you or to other of his suppliers could save a life.