This is one of those hot topics. Everyone has a different reaction to ads. If you are adding it as directed when changing water, it is hard to see any harm in overdosing.
But then I question why I need to add something to improve the normal fish design. I find that one way to make the fish produce slime is to add salt. The salt irritates the fish and it produces more slime coat. But is it a good idea to irritate a fish to get this done?
I prefer to let nature do it's thing and me not irritate the fish so that he is stressed and needs a thicker slime coat.
I reject products that try to trick me with advertising hocus pocus. Your decision on whether to continue buying that product. Myself, I go for a very simple one step product that does only what I want without adding bells and whistles to confuse me.
Clean water and no stress is the best fish medicine I've found. I'm open to other information but only if it is not from people trying to make money.