how can you tell it is still charged after two years?
Years ago Arizona Ice Tea put their memory tonic in blue bottles. Before they took it off the market I bought all I could find. My laser beam doesn't shine through the blue so I pour some off into a glass and keep it in a dark place, wait a few days and shine the beam through it.
Whe someone wants some I give them a fresh bottle, dig out an old bottle and check it out.