For most of the packages you'll want to keep them at a specific version for each virtual environment, however for packages such as pip, you may want to upgrade it to the latest version in all your local virtual environments. If you're running virtualenvwrapper, all you have to do is use the allvirtualenv command:

$ allvirtualenv pip install --upgrade pip setuptools wheel

And inside every virtual environment you'll have the latest version of pip and the other essential package installation tools updated in your virtual environment.