I personally like to always have a link where list members can go and buy something, just so people get used to it. What I've found is if you have too much stuff that is strictly content without any link for people to take it to the next level and buy anything, then when you do pitch something, people get angry and unsubscribe from your list. Whereas, if you always have a link and just give them the choice of buying something, they get in the habit of clicking and buying things from you.
What I would recommend is something in between. Have a good content-rich article, a tip, or a suggestion that teaches the people in your list X-Y-Z. Then at the end of it say, “If you want to learn more about "list building," for instance, click here.” That's not really a pitch, it's a suggestion. It's more recommended reading. It's a recommended resource. It's not a hard sell.
It's very powerful! If you go and buy an ebook that you're going to be promoting to your list, for instance, what you do is you read it, and then you say, “I was just reading in a book,” or “I just got an e-book and it is absolutely awesome. It taught me something beneficial about "list building." Here's what it taught me, and why it's going to change my life forever. If you want to get your hands on this book, here's the link.”
If you want to increase the power of that strategy, send an email to your list a couple days before that and say, “I just found out about this awesome website selling this e-book about "list building" and I've decided to purchase a copy. I'm going to read it over the next couple of days and will let you know what I think.”
Tell your list members that you're going to purchase it or tell them you just purchased it. You'll tell them in a couple of days what your thoughts are and how good it was. They will be expect an email from you to tell them how great or how crummy it was. The tactic builds anticipation so they pay attention when they get it.
And it's perfectly okay for all of these messages to be in a sequence. Even when people opt-in to your website in two years, they still get the sequence in the same order. That's okay; there's nothing wrong with it. You're still delivering content and information, which is what they are looking for. Does that make sense?