RBC said:
Of course, it would be best to communicate with them at least once a month, if not every week. Maybe twice a month etc,
Wow, that would be the quickest way to get me to unsubscribe from your mailing list. Seriously.
When I sign up for an author's mailing list, I expect it will be used for potentially three things:
1) To notify me of new releases
2) To notify me of special sales
3) To notify me of an opportunity for readers to enter a contest
If you're sending me long chatty newsletters once a month, twice a month, weekly for no reason other than you feel like you need to stay in contact...yikes!
Seriously, I want to know when your new book is out, and that's about it. If I want to hear from you on a regular basis, then I'll "like" you on Facebook or follow you on Twitter. Send me much more than that and I consider it spam, even if I signed up for it in the first place.
I specifically state on my sign-up form that it's for readers to be notified of new releases only, and I consider that a selling point. Nobody wants to get tons of newsletters.