I believe it will depend on what your requirements are.
The .qvw file will also store the internal data model, after script execution. If you need to keep the data, I think there is not much that will decrease your file size, since the data is already quite well compressed in the .qvw file format. An additional compression by e.g. Zipping the file won't probably shrink the file.
If you don't need the data, i.e. you are able to reload if needed, you can use
File -> Reduce Data -> Remove All Values
to strip the data and save the file.