The autoresponder series is one of the best tools for generating a passive income (even on a blog), because if setup properly, all you need to do is generate more leads and your pre-written emails will take care of the rest.
The goal of any list is to stay fresh enough in someone’s mind so that when they decide to read one of your emails (and most people won’t read many of them), they remember who you are and that you have given them a lot of value in recent weeks.
From my experience...
I recommend you keep your autoresponders pegged at between 5-7 days. You can send them a bit more frequently, but remember that you will also probably want to send out broadcast emails with special promotions and new products. If you already send them a message every 3-4 days, you risk oversaturating their inboxes.
Once a week keeps you fresh in their minds, offers regular, predictable value, and ensures that when you do send a broadcast, they will at least look at it.
Personally, I don’t believe that clicks are more important than opens. Maybe in the long run, but from message to message I’m much happier to see a high open percentage than click percentage. It means I’m creating a relationship with those readers and they are more likely to click something later. If a message gets a 65% open rate and a 5% click rate, that’s much better (to me) than a 30% open rate and an 8% click rate.