I understand that your external drive has both USB2 and FW800 connections.
Refuses to connect with FW but with USB2 works but gives times which are really too long even for USB2 and 191GB.
Question is why it does. According to your info I agree the MAc is OK and as John writes it should be the disc.
Can be the cable or the FW electronic in the HD but may be also the USB electronic Or the HD itself ?
The 24 days will probably reduce and do not affect the Mac but what about the HD ???
If it is in bad conditions will it survive 3 weeks of continous running ???
I hope to be wrong but. If the picture in that disc are the only copy you have I would open the disc and put it into a fres new enclosure with a fast connection which your Mac can use (FW800 or eSata or Thunderbolt).
If you think to go in this direction let me suggest this YouTube http://youtu.be/1Aa3BXmQVpc
That data rate is so slow that it cannot possibly be writing to the HDD nonstop. In fact, it will probably spin down and your Mac will go to sleep unless you set your Energy Saver to "never sleep".
This problem would be unacceptable to me. Shut down your Mac and use FireWire. The disk will unmount safely. If it remains slow with FireWire I would question the disk's integrity. It is likely to fail completely, well before the data finishes copying.
Update: Afer about a day and a half, the external drive started to spin faster and the time reduced from 24 days to a week, then days, then hours. It finally completed. After it completed, I plugged in the FW to move my iTunes folder and it's moving at FW speed. Something is definitely wrong with the external but I've now backed up all the data. Thanks for your help!