The shelf life of a stock solution mixed in TEA should be at least 2-3 years unless the solution is contaminated. The same is true of stock solutions mixed in glycol. This is because because the solutions do not oxidize as they might if mixed in water.
Originally Posted by PhotoJim
Some people have suggested that such solutions might last for decades. I have some doubts about this because all of the solutions I have mixed in TEA, including Gainer's original PC-TEA, have strongly discolored after three or four years. I also have a small container of another single solution pyro developer that I mixed in TEA several years ago and the color, which was very clear on mixing, has also strongly discolored in the three or four years since I mixed it. I don't know the cause of the discoloration but tend to believe it is caused by oxidation.