How long (time/duration) should a complete restore on an iMac from Time Machine take?
After reading some Apple support threads on this topic, I found a hopeful tip that (for some reason) connecting the TM drive before launching Time Machine System Restore limits you to USB 1 speeds (and thence multi-day time estimates), but attaching it after gives you full USB 2 speed.  

After suffering through about 1% of a backup estimated at 60+ hours to complete, I tried this and it indeed the projection is much better.