I think most people are reasonable and patient, and can understand delays. And I have not seen anyone question his honesty or integrity. However, I think that it is the lack of response, rather than the delays, that is most disconcerting. A quick reply - "I'm sorry, but we are so overbooked that it will probably be 3 months before we can fill your order" - would be satisfactory, and would probably result in a significant decrease in the amount of email inquiries, giving him more time to work on those orders. Anyway, it is what it is. There aren't so many options, so you either accept it, or do without...