You never really learn a language, and you never really are an expert in using it.
While you may know a lot about what the language is, how it works, and accepted ways of using it, your opinions on how to do things will always be evolving (hopefully).
Sometimes all the experts who use a language will be behind the times. For a long time experts championed strong OO design. Now all the experts champion hybrid OO/FP style things (witness Java 8!).
This too shall pass, and we should have the humility to realize that no-one knows for certain what will be the next evolution of software development.
While you may know a lot about what the language is, how it works, and accepted ways of using it, your opinions on how to do things will always be evolving (hopefully).
Sometimes all the experts who use a language will be behind the times. For a long time experts championed strong OO design. Now all the experts champion hybrid OO/FP style things (witness Java 8!).
This too shall pass, and we should have the humility to realize that no-one knows for certain what will be the next evolution of software development.