I write and publish a post every Monday and Thursday. This has been working well for me so far, and so I plan to keep with that schedule unless a better idea comes up.
Monday articles are available to all email subscribers (Paid and Free).
Thursday articles are available to only Paid email subscribers.
In the longer run, I intend to do other things with the paid subscriber list, but I don't know what those things are. So I don't want to over-promise and under-deliver. Instead, I can just say that I have great intentions, and we'll see what happens.