Facebook can be a powerful tool, but it can also be a royal pain to manage. Just because someone "likes" your page does not mean they get to see all of your content. The more they interact with the page with likes, shares and comments, the more posts they see. I am an administrator for a page that just passed 2000 likes. When I post something, Facebook shows it to a few hundred people. When those people start liking and commenting, Facebook shows it to more people (their friends, plus presumably more of the page followers). Still, some posts never pass 1000 views even though we have 2000 followers. My most popular post got over 20,000 views.
Anyway, my point is that you can't count of Facebook to be a reliable way to spread information for the average user who isn't going to interact with your page.
If you want to see all of a business/organization's posts, you have to use interest lists. For example, if I wanted to follow Paul's Facebook page, I would click "like", which gets me another menu, where I click "add to interest lists". Then I would add it to my gardening list, click "go back" and "unlike". That gets the posts off my personal wall, so they aren't mixed up with family stuff, and when I view the gardening interest list I get to see every post, not just the ones Facebook decides to show me. The negative from your point of view is it doesn't show up as a "like" (as far as I know). Your average user is not going to bother with interest lists.
Now, to actually answer the subject question, I can tell you that I follow pages if they post useful content or links (a catchy photo helps) every day or so. More than that is overkill. Some bloggers put a post on Facebook every time they do a blog post to get me to click the link and go there, which is useful if they don't have some other way to let me know that. You have the daily-ish email that serves the same purpose. Some bloggers have contests that require that you like their Facebook page to be entered for the prize. Most that I know of use Rafflecopter to manage giveaways. If your goal is more likes, that can help. If the goal is to get people to sign up for the daily-ish email, which will remind them to check permies for items of interest, the number of likes should not matter as long as people are finding the page.
This is my first post!