If you want readers to keep returning, activity is a must. Are you keeping your blog as active as you should? No matter what your site is about, it needs to keep moving.
Many find that having a blog is the easiest way to do that. There are only so many updates you can make to informational and product pages. But a blog can be updated as often as you are able.
Just remember to keep your blog flowing for the most reader activity as well.