I would highly recommend the reading of the article connected to this link by every Forum member.
http://acrylictankmanufacturing.com/blog/shocking-truth-nitrifying-bacteria-products-colony/
Even though it is presented by a manufacturer, it is, by far, the most accurate, open, and frank presentation concerning 'beneficial bacteria' products that I have encountered. Most questions and doubts are addressed in this article.
I think we should keep in mind the purpose behind bacteria in a bottle products.
Is the product to be used for starting a pond or aquarium, or is to be used for ongoing " maintenance"?
Ongoing maintenance bacteria addition is completely unnecessary.
I can see where using a product with live bacteria would be helpful in an emergency startup situation, but the bottled bacteria product would need to be from a reliable source. Even then, the manufacturers recommend water changes as a method of diluting ammonia buildup when detected.
It's not an ideal start for fish.
There are only 2 distributors I'm aware of that date stamp their products, ATM and Dr Tim's.
Proper planning when setting up a pond or aquarium is far more desirable.