Supercharging regularly at full rate is (now) known to stress the battery to the point where Tesla apply limits. Most of the time owners want to charge as fast as possible and be on their way, however there could be occasions where absolute speed is not the most important factor - maybe I'll take lunch not just a Latte. So, if a supercharger site is not busy, why not permit owners to select a slightly lower max charge rate (eg 80-90%) to help mitigate repeated fast charging effects. Tesla know how busy a site is, so even if it got busy whist a vehicle was there, they could just override the lower setting and charge as fast as possible. The mobile app as always will announce when almost charged so the owner is still informed whenever the charge completes. Just a thought.