My thinking about build time with SSG was right. As content needing to be pre-rendered at build time goes up, so does the build process length. I stumbled upon a great piece about this issue, "The Problem with Static-Site Generation" and it goes into the concept of ISR, incremental static regeneration. It also bring up a good point about using a CMS to back your site content, and not wanting to run a full build after publishing content. ISR can help olve this.
Here's the article with all of the good content: A Complete Guide To Incremental Static Regeneration (ISR) With Next.js