If you mix with distilled water, it will last for a long time. I usually keep a revolving batch that I add to whenever the level gets too low, 1-2 gallons at a time. If the pH goes above 3.5, you can add a couple of drops of undiluted StarSan to bring it back down. And when it gets too much debris at the bottom of the bucket, you can rack it off into a new bucket.
Only once or twice a year do I actually dump it out and make a fresh solution. I have also never experienced the cloudy StarSan that I hear people talk about, so I guess distilled water is working.
Read my brewing blog here! Last of the Zyme Lords
BOUSIRIS BOUERY - Home of the Zyme Lord
The cans of Leinenkugel's had masking tape on them with JOHN'S printed in ink. Amy looked around me and said, "John is protective about his beer, isn't he?"
"I put that label on there. When company comes I want them to know the Leinie's is his, not mine." - David Wong
Anna Livia Irish Stout
Melancholy Bill's Infinitely Sad Pumpkin Ale
Lucian's Landing Ginger Metheglin