I use a spray bottle with star san, so I don't use a lot of it each time I brew.
Is it okay to store the rest in a bucket and then refill my spray bottle when I need some?
I've read that it should be okay if the pH remains below 3.0. If it goes above 3.0, should I make a new batch of star-san or just add a little concentrate to the mix to bring it back in line?
What if the bucket starts getting mildewy? Should I throw out the batch and make a new one?