"Stock and flow" describes a theory of content articulated by Robin Sloan. Sloan emphasizes the importance of maintaining a library of reliable content that is durable and evergreen. This is "stock," and drives the long-term traffic to your channel or site. The stock must be balanced by the flow—the frequent, ephemeral updates that help the creator maintain a profile among their audience. To grow stock, collect, organize, and expand on your flow content.
Kleon, Austin. Show Your Work!: 10 Ways to Share Your Creativity and Get Discovered. New York: Workman, 2014.