Having said that, what are common frequencies?
Most marketers mail about 2 - 3 times per week. Many mail once per week. Less than once per week, and you are probably losing people's interest.
More than 2-3 times per week, you tend to get many more unsubscribes and unhappy people.
Having said that, I mail practically daily. Why? I make more sales that way. But you have to keep in mind - I get between 50 and 200 subscribers per day. I can afford to lose 10-20 people per day who unsubscribe. My feeling is, if they do not like me, they will never buy anyway, so who cares?
But if you are only getting 10-20 subscribers per day, you can not afford to lose 10-20 per day.
Another consideration is this: I work fulltime online. I can afford to spend a couple of hours per day writing emails and email campaigns to keep up with an email or two per day.
If you are only working this parttime, and you only have a few products or less, you can not mail everyday. You simply do not have the time! You have to have time to not only create new emails and email campaigns, but you have to time to recruit new subscribers, time to create new products, etc.
So what is best for you?
If you are new online, 1-2 times per week is probably plenty.
If you have a few products and you have some experience, you can go with 3 emails per week.
If you are going to do more than 3 emails per week, you need to seriously think through the time commitment and the stress on your list. You will get more unsubscribes ... are you willing to lose them?