Star San and distilled water

[Buffers brewery]

You've asked for it!

Is that a question @peebee ?!?

 

[peebee]

Is that a question @peebee ?!?

I'll deal with you another day. (Grumph, grah, neaaar, ..)

 

[peterpiper]

I just use tapwater and always have a big bucket of it ready made from purging kegs and things....keep it for months and ph is always low enough for it to be effective. Usually only refresh it when it gets a bit mucky.

I'd refresh a large batch, just by adding more Star San or equivalent, rather than throwing it all out. Unless it's likely to have picked much organic matter on the way. Just aim to keep the pH low.
Storing out of direct sunlight, should increase the shelf life.