Turn off file watching in Meteor
I don't think it is possible as for now
Even if you could stop to watch it would not solve your issue
When meteor detect a change it rebuild the server (.meteor/local/build/) and serve it from there.
Public folder is sent there : ".meteor/local/build/static/"
In a case where you would stop watching for updates you would also stop to see changes in what your client can access.
I found out that this particular case can be solved by replacing meteor by another tool to deal with static assets.
I have a meteor app to deal with data and file sync, but I also keep an Apache to serve as a file distribution manager.
My meteor app keep small, assets can be sent somewhere else (Ex.: S3 when you get in production).