You only need to keep studying another language should you be required not to adjust your thinking when switching to that language. If you don't need to work in language X next week, then why waste time reading about it? Focus on what you're doing in the now.
I have to work on two projects constantly. One is in
C# and the other is in
PHP. These two projects communicate with each other. So I'm often programming in one or the other. As a result, there is no start up time required to program in either language. I can just sit down and start writing code.
In this same project there is a command line tool developed in native
C++. I only perform maintenance on this project once a year. I try to allow a back log of issues to build up before starting work on it. This ensure that I can commit myself to working in
C++ for a fixed period to complete multiple tasks. Part of my estimating to work on things includes time required to
start up again in
C++. I have to force my brain to think in
C++ again and that sometimes takes a few days to fully kick in. I start with simple tasks and progress to harder ones.
What I can not do, and have sometimes been forced too. Is constantly switch languages. This creates extra fatigue in my head. Each language has it's own does and don'ts. It's own flavor of approaches and sticky catches if you don't fully know the language. If I constantly switch languages then I run the risk of not really knowing that language well.
The best advice I can give is not to mix purpose. Use each language for what it's good for. Otherwise you become frustrated because one method is quicker/easier done in the other. This becomes a distraction and opens the door to second guessing an implementation.