I just came across vbrfix, a very handy tool to fix MP3 track lengths that seem to be off, which according to the manpage can be caused by bad VBR encoders. Like ancient versions of Windows Media Player, as I only ever had this problem with one album and I probably ripped that when I was twelve. (Just kidding, I didn’t even have my own CD player back then, much less MP3.)
Usage is a no-brainer, messed up MP3 goes in, shiny new MP3 with correct track length pops out. What I didn’t try yet is in-place corrections, but that probably works fine as well.
Why would you want to do this, other than OCD?
Well, it appears to throw off Last.fm scrobblers quite a bit. Say Banshee sees a track that’s 25 minutes long and finishes playing after three minutes: “less than 50% played” = no scrobble. I know. This results in precious track plays being lost for bands that deserve a lot more exposure.
Which is still OCD, now that I think about it.