I find it hard to understand why they would provide the various methods of checking the viability of the product once mixed if they are actually stating 1 hour
As I stated previously, legal protection. My guess is that Five Star can fully guarantee that Star San is fully effective for 1 hour, but not beyond that. It's likely they have a requirement to kill X% of organisms within the 1 to 2 minutes, and if that kill rate drops below a threshold, they have to limit their claim.
Here is one possible explanation for the difference between the manufacturer and retailer claims -- keep in mind this is an illustration that I made up.
Let's say the threshold for organism kill is 95%, e.g., within 1 hour of mixing, Star San kills 95%+ of all organisms with a 2 minute contact timeframe. [I have no idea what the actual number is.]
After 1 hour the mixture degrades so the kill rate drops below 95%, and Five Star can no longer make the guarantee.
Over the next 3 to 4 weeks in a sealed container (spray bottle), the mixture slowly degrades to 50% kill rate. For home winemakers, this is acceptable. Why? We have cleaned and rinsed our equipment, so most organisms are dead and/or removed. The Star San eliminates at least half of what remains, reducing the organism populations enough that they cannot successfully reproduce enough to cause problems. Since the wine suffers no ill effects, the Star San is fully successful for home winemaker needs.
Keep in mind we are not sterilizing anything -- sterilizing is 100% kill. Sanitizing reduces the organism populations enough so they are not a problem.
Another explanation is that one person said, "well,
*I* think that Star San is good for a month,", and everyone else parrots it.
The folks that are keeping Star San for 3 to 4 weeks? If you are satisfied, keep doing what you're doing.
IF you also read their FAQs you will see that it's not safe for pets.
According to the product fact sheet -- undiluted, Star San is harmful to the skin -- which makes sense, it's acid. So it makes sense to keep it away from pets. And children. And yourself.
My son looked at the formulation for OneStep, and said it's essentially industrial grade H2O2. He couldn't be sure it was harmful to the skin, but strongly suggested that if I get splashed, to rinse off. Better safe than sorry!
This is equally true for all the adjuncts, cleaning, and sanitizing products we use.