Advantages of Using a Monorepo?

Hi folks. When building a site with Sanity and Gatsby, is it standard to do this as a monorepo of the two or to keep them in separate repositories?

Both is fine. But with monorepo, you can have an easier time deploying (1) testing and bootstraping both project, in exchange for slightly more complicated setup.
1.
Lots of static host provider offer support for multi site, monorepo build

Thanks Appreciate the advice.