I have re-used my Star-San in a bucket with lid a week later but never keep it past that.
Always dump, clean then re-create if past a week.
No issues yet using that method.
Stick to the recommended dilution.
GENERAL USE DIRECTIONS
All surfaces should be cleaned and rinsed before sanitizing with STAR SAN.
Directions: A dilution of 1 ounce to 5 gallons of water, STAR SAN will provide 300 ppm of dodecylbenzenesulfonic acid. After 1 to 2 minutes contact time, drain sanitizing solution equipment thoroughly. Do not rinse. If using Star San in CIP, proper water balance must be maintained or your pump may cavitate. If used at a rate of more than 300 ppm, a potable rinse is required.
Part Soaking: Use 1 ounce of STAR SAN per 5 gallons of water. Parts must have contact with solution for 30 seconds and put on wet. When solution begins to cloud, sweeten with Star San or Phosphoric Acid. Solution must remain at a pH at 3 or below to maintain proper sanitizing level.