Hello,
if you separate the development substance together wit sodiumsulfite from the alkali (Borax) you have nearly the formula of a D-76 2-bath developer. The life time of solution A is very long without the borax and is determined mainly by the carry out of a small volume with each film. The oxidation of hydroquinone and metol by air is faster at higher pH values. There are many formulations in the old literature based on stock solutions.