I'm meticulous about tagging and backing up MP3s for different mixes in car stereos and other devices. One problem is that I have so many MP3s and different copies I don't know which are tagged and when they were ripped. I prefer to retain the file's modified date when I just update tags so I'll know how old the rip is - bit rates have increased a bit since last century.

I wrote a Powershell script that sets the date a minute newer when it updates ID3 V1 tags so I can compare files and know that one came from 2005 and has had metadata updated since then. I haven't found a bulk tagger that does this.