I might copy the library to a spare Mac and let that one run instead. Or write up an Applescript to try to speed things along -- I wonder if an Applescript or an Automator workflow can be written to play only the first few seconds of every track.

There's an Applescript that will check your library for missing tracks. It takes a few minutes, not hours or days - it's very helpful. I assume it will still run under the latest operating system - I'm still running Snow Leopard and it works on my computer.

Try Doug's Applescripts web page - http://dougscripts.com/itunes/

Karen