I recall that rose, who is the original poster who brought B12 issues publicly to this board and it predecessor, said it was taking years for her to recover.

If you have severe damage, recovery is slower, and may not be complete if nerves have actually died.

For example in Japan where the terrible accident occurred with Vioform (clioquinol), people were permanently damaged, and blinded due to low B12.
http://www.multinationalmonitor.org/...mm0493_11.html

This devastating accident led to Japan being very aggressive in treating low serum B12 levels. They typically treat below 500-550.

So I would say recovery depends on how severe the damage has become.