The battery has definitely aged; and I could never get the original advertised range on the highway (not even close). I'd say it's lost about 20% (or slightly more) of its original capacity in about 5.5 years. According to the Tesla degradation charts, I'm above average in terms of degradation, but still within "healthy battery" standards. I find it strange that I'm above average. I try to keep the battery in its happy zone and I'm fairly conscious about it. The car has almost never sat below 30% or above 80% for more than a few hours. The car is charged indoors in my garage and is always plugged in (Tesla recommends this). Supposedly, after this, there should be almost no more degradation. As the bulk of the degradation is accelerated in the first few years of the car.