With this tool you can convert Collada models to Threejs' own JSON format. The JSON format is not only much smaller in file size (50 - 75% smaller), it is also easier and thus faster to parse by Threejs.
To be able to save the converted JSON files automatically:
navigate to chrome://settings
click "advanced settings" and scroll down to the "Downloads" section
untick "Ask where to save each file before downloading"
you might get the message "This site wants to download multiple files", click "Allow"