I'm going to chime in here as I've been in a very similar situation. They accept our money, we have entered into a business transaction; at that point all deals of "I do this in my spare time" or "it's a hobby" are off the table. I will accept that things may come up, but when I ask for a specific time, I expect my product in a relativity close proximity to that specified time frame that you gave. I will also not accept a second rate product as I have paid for top notch. An excuse of "I do this as a hobby, it's not my real job" will not be accepted as see: Business transaction.