Progress bars

I recently saw Liw's "Progress bars everywhere!" and now again I came across a related thing that's always been nagging me. Burning CD/DVD discs, the progress bar works fairly neatly until the end. Then it takes forever in some finalization and fixating phases.

How hard could it be to make the program record wall clock time for certain size disks and in particular how long those final stages take? At least a guess. I believe that time would be a fairly consistent value and measuring it for a given system should take out drive differences. Then you could put this in the time remaining bar and let that tick down. At least on handwaving level that sounds trivial and it would be immensely nice if that estimate did tell you when you can come back and your disc is done instead of when you can come back and stare at an unmoving progress indicator.