If there's a patch to the major driver version you're using—for example, 550 recently got an update despite not being the latest—that tends to come in relatively quickly. Actually updating to an all new version of the drivers doesn't happen very quickly though, partly because Nvidia driver updates have been known to cause problems in Linux, especially for Wayland users. To be honest, I'm not sure Zorin will ever switch you to a new major version on its own.
If you want to change driver versions, you can do that by running Software and Updates, going to the Additional Drivers tab, and changin the driver version you're using from that list. If you don't see the version you want, you can follow Aravisian's steps here:
That requires terminal use, but is the most reliable way to update to a major version Zorin has yet to deploy. I strongly recommend against trying to install Nvidia's drivers downloaded directly from Geforce.com. That way lies frustration and possible system breakage.