Hi @TORLEY, great question!
It’s not documented but I did some testing and it appears to automatically sync about every 9 minutes or so.
As you already discovered, it is possible to manually sync a data source in Central so it may be best to manually sync it if you need it to refresh things a bit quicker. Though it’s worth noting that as Central is in currently in “public preview” it's still under development so some things may change on that.
You can learn more about using Central’s data sources here: Add a data source to a Zapier Central bot
Hope that helps to answer your question. Do let me know if I can help with anything else. 🙂