How long after you activate MMS must it be used?

In the book that I read (cover to cover) it talks about activating MMS then using it after the proper wait time, 30 seconds to 3 minutes based on the activator used.
How long will activated MMS remain active? A friend of mine says up to week- is this correct?
Does it start to dissapate as soon as it is activated or does it need to be ingested to start that process?

My experience has been that if it is covered and in a dark bottle it lasts and lasts - about 2 weeks but you can always check with a pH strip. 5-5.5 ideal.