<< If doubt if we make any ourselves.  What we do seem to have are different
 capacities to store it.
  >>

I dont have access to my references on this, for years it was taught that all
vegans would be B12 deficient. The reason that  the time varies so much in
observing deficiiencies in some is that it is made in the colon in healthy
people. Vegans don't have deficiencies unless there is a problem in this
system.   I still am sure that the storage time for B12 in the body is less
than one year. I have known  vegans that have been vegan for more than 20
years with no B12, certainly if the old idea that B12 could not be made
somewhere in the body, then it would be needed. As it is those with digestive
disorders, or taking antibiotics need  to take B12, and if the signs of
decifiency develope then they should take B12, but the truth is that we,
actually not we, but normal flora in the colon, make B12 and we absorb it.

Jerry