I don't think you're going to master something. You're doing to dip into a stream, get some skill and competence, and much of that will continue to be valuable over time. However, sometimes there are substantial changes to tech in the stream, and it is possible that you may find some of your knowledge is old and not optimal. You'd have to dip back into the stream again and learn more.
How you do that, I have no idea. I agree, that doc'ing and searching isn't always helpful and out of date. It's one reason I think versioning and dating of both technologies and modules/blogs/etc, is really important. Some vendors have resisted versioning things, and giving a way to match up a point in time with knowledge. Teachers/bloggers/etc. also often don't think through anything beyond a publish date, rather than a version or a "observed" date for the portal or the PowerBI Desktop, or something else.
It's a hard problem, and worse in software, but it's going to be an issue with other things as well. If Tesla allowed 3rd parties, or we start to see them, I think mechanics will have some issues with different "versions" of how the car works or is diagnosed. Already, there are constant technical documents published for cars because what exists in the first version of a new car might be different after 6 months. Not lots of stuff, but particular parts might change. They have the same problem, at a different scale and rate, but it's always a problem. I see this same issue sometimes looking at YouTube with my car. It's a 2012, listed as the E70 model, but the way certain things work or are put together (or come apart), can vary, so hunting for knowledge on YouTube or elsewhere is always a challenge.
I think search and find is likely your best skill in continuous learning.