I found an (open) bag of one step cleaner that's at least 2.5 years old. My first reaction was to toss it, but I thought I would see what everyone else thinks first. Does this stuff go bad?
Once opened most of the oxygen based cleansers only last about a year, unless they are sealed tightly and stored in a temperature controlled environment, like your home. If it was in the garage, I would definitely toss it.