It’s good that you update your extensions. Would that everyone did. If you’re using the Extension Manager and the Sketchucation Extension Store tools to install extensions, they will do the majority of the work and make sure you have the latest extensions.
As for migrating other stuff, I have all of my local components, materials, and styles collections in the User/App Data/Roaming… folders and when it comes time to update to the next version, I simply copy the folder and paste it in the corresponding location for the new version. Example–my SU2018 Materials A folder.
I copy Materials A from SU2018 to SU2019. Done.
The main thing I wish they’d do is come up with a tool for replicating toolbars. Until that happens, I just make a screenshot of the previous version showing the toolbars and import that into the new version of SketchUp as an image so I can use it as a guide for custom toolbars and toolbar placement. It works well enough and saves going back and forth between versions.
If it had been you, I’d never let you forget it.