When sending messages to your list, it can be an advantage to have a predictable pattern. If you normally send one message per week, please don’t suddenly send out 10 messages in one week.
And, remember if people are actually reading your emails (that’s the goal, right?), they will get used to receiving them on certain days. Do your best to stick to the same schedule.
I receive a certain e-letter every Tuesday and Friday, and do I notice if it’s late? You bet.
If you are late with your message, please be polite and apologize or give some kind of explanation. Think about it, you are dealing with human beings on the other end.
People love routine.
Also consider the format of your emails. If you have any kind of structure at all, follow the same pattern every time. I receive e-letters that usually contain a quotation of some kind, and I expect it to appear at the top of the screen, because that’s where it usually is.