To install this package, run in Emacs:
M-x package-install RET persist RET
This package provides variables which persist across sessions. The main entry point is `persist-defvar' which behaves like `defvar' but which persists the variables between session. Variables are automatically saved when Emacs exits. Other useful functions are `persist-save' which saves the variable immediately, `persist-load' which loads the saved value, `persist-reset' which resets to the default value. Values are stored in a directory in `user-emacs-directory', using one file per value. This makes it easy to delete or remove unused variables.