My airpods are 2 years old, always used as a pair, and when one of them gets into the red with under 10%, the other still has 39-40%. The difference was already there maybe 15-20% when they weren't a year old, I went to Apple and they said it was "within spec". Bullshizzle if you ask me.
But yeah, such is life with expensive disposable products, because the headphone jack was so bad.