This has been marked by Kory Kramer as a Duplicate of Overwrite existing Tile Layer Service on ArcGIS Online. Please visit that idea to up vote and comment. Thank you.
There is no option to overwrite vector tile packages in ArcGIS Online where we (Texas Department of Transportation) publish our Statewide Planning Base Map layer. Since we have multiple, high-priority web applications that consume this basemap, updating the basemap service comes with some risk that is uncomfortable for us. Currently we update the vector tile basemap weekly, during off hours when usage is low. This requires that we delete the current vector tile basemap layer then publish a new layer with the same name, so that code changes are not required in our applications every time a new vector tile basemap layer is published. During this time, all of our mapping applications are down.
A better option (especially given how much Esri is promoting the use of this technology) would be to allow for overwriting, the same as is available for other vector service layers.
One additional note is that we would like to be able to do this for our internally hosted (ArcGIS Portal / ArcGIS Server) vector tile basemaps, as well as our externally (AGO) hosted versions. There is a script that helps with this process on AGO, as discussed in this thread ( How to update Vector Tile Layer? ), but none for ArcGIS Portal.