I've been using my bleach oldest first, but I got to thinking to day and wondered if I'm doing it wrong.
Since the highest concentrations lose the most strength, shouldn't I just be using the highest concentrations first? So, 10% before 8.5% and use the freshest stuff first when the initial concentrations are the same.
I know I'm probably over optimizing, again, but I already sort the bottles when I buy more, then just use them from one end. It isn't much effort.