Advantage Arrest is prone to evaporation and light sensitivity.  As the ammonia evaporates, silver will crash out of the system leaving black flecks at the bottom.  Typically this happens slow over the course of many hours so it's possible to dispense early and use later in the day.  Light however, will be the major issue.  Strong lights can cause it to crash in just a few minutes to hours.  So, as long as they keep it dark, it may work.  Have them experiment and see how it goes.  If they start to see black build-up, it's going bad, if not, it's still good.  Also, a significant amount of black needs to build up before it's out of specification.