Question About Clickbank and Email Marketing

I'm in the process of setting up an email marketing campaign where I will promote Clickbank products. My auto-responder is setup to go something along the lines of:

content - content - offer - content - content - offer ...etc

To those of you doing this type of thing, do you include affiliate links in any of your content emails? My offer emails are obviously promoting the products using email swipes with multiple links. However, I'm wondering if I should try to squeeze one link here or there in the content (or at the end) of some content emails. Would this be advised, or should I only include affiliate links in my offer emails?

Thanks!