Get some low pH-range (2-5ish) test strips. They're cheap - a lot cheaper than more StarSan. As long as they're testing in the low-3 range, you can keep using it.
At the rate I'm going (4 batches plus bottling since i mixed it up last?), I'm thinking my 32-oz bottle of Starsan will last me...
First-timer here. I started an all-extract Dunkelweizen on Saturday. My local brew shop offers liquid or dry yeast options, and I picked the dry for this batch because the location I had planned for my primary fermenter is in a very cool basement more in line with the temp recommendations for...