I only really change out the star san solution when there is a fair amount of crud collecting in the bottom of the pale. Otherwise, it is good to go.
Yep. With distilled, it stays clear - more the matter of collecting crud in the bottom, as said.
That's what I do. I buy a gallon of distilled water and add .25 oz of sanitizer. I fill a spray bottle for spot sanitizing and the rest goes into my fermenter. I shake that several times throughout my brew and then drain it back into the gallon jug right before I add my chilled wort.