@Mortie31. I use 12 percent - and on the packaging it instructs to refrigerate it after opening. The brand I use comes in an opaque bottle. Here is a nice quote from an article that goes over this:
"Hydrogen peroxide is relatively unstable and decomposes quickly.
In a sealed container, hydrogen peroxide lasts approximately 3 years. However, as soon as you open the container, it starts to break down. You might be surprised to learn that it’s only effective for 1 to 6 months once the container is opened.
To ensure it lasts as long as possible, store hydrogen peroxide in a cool, dark place. Don’t open it until you need to use it, and when you do open it, keep it in the original brown bottle. The bottle is designed to prevent light from making it decompose faster.
When you’re using it, make sure the liquid that’s left inside the bottle doesn’t come into contact with anything else. For example, don’t dip your finger or a rag into the bottle. This could make it decompose faster."