Years ago I did a 'simple' file server migration - windows 2000 to windows 2003. (or it might have been NT to 2008).
But I took the opportunity to scan the shares and build a histogram of file count vs age, so we could go to the business with the analysis "do you really need this share?" and have a bit of a tidy up.
One share had files with the newest date of 95 months ago.... so I went to the business with my spiel "hey these haven't been touched in 95 months.... etc"
The business came back "95 months....???? Oh, that's 8 years. Oh yeah, that share was for a project that shut down 8 years ago, so yeah that'll be about right"
me: "oh cool - dont need it any more then"
business: "ummmmmm...... if we did, could it be restored and how long would it take "
me, internally: "FFS!!!!!"