One Step works by producing hydrogen peroxide in the solution, so the most important thing is to keep in mind that peroxides are degraded by organic soils, light, and heat, so if you keep your solution away from those things, it will stay better, longer.

In a sealed, dark, and clean container, the solution will last up to 1 week.

In a closed, clean container in a refrigerator, the solution is good for over a month (but let it warm up before you use it).