I've been involved in a site that has over 10k pages and it worked fine. Sanity has a preview feature and Gatsby incremental builds are available now (which I haven't used yet) but should bring your build times down significantly.
We use Gatsby preview. It frustrates me that we are paying a lot of money for a substandard solution to a problem that shouldn't exist.
The same goes for Gatsby incremental builds. We don't want to run a web server, so instead we should pay to run a build server 24/7 so we can have a warm cache available when we need to build!?
The annoying part is that there is not reason a static site generator should have these limitations. Gatsby's entire revenue model is based on solving problems that only exist because of the bad architectural decisions in their open source product.
