There is an issue with arma that keeps the process running even after closing the game. If you do this too many times, it might result in lower performance.
2 things you can do is either close these processes from a process manager like "Process Lasso", "Process Explorer", or "Process Hacker", or you could restart your PC every once in a while.
You can always try to change your memory allocator and extra threads that arma uses through the launcher. You'll have to look up which are the best for your computer, but this might help.