[Histonet] Hematoxylin stability

[Hana Peter]

Hi,
I recently came into possession of a small amount of hematoxylin powder
and for the first time I'm going to make my own Harris hematoxylin and 
maybe some Mayer's too.
As I have a limited amount of powder, I need to be extra careful with my
supply.
Does anyone have experience with "home" made hematoxylin and its stability?
I found on the internet that the stability is up to 6 months. Is this
really true?
Thanks a lot!
Hana Peter