Lol, they don't always reset mileage, sometimes it's just dash preferences, but if the battery voltage goes too low in storage I've heard of it happening. Aprilia replaced some whole dashes on RSVRs to try and solve the problem but some people still lost mileage. There's things I can do to improve charging of the battery when it's started, I've just been too lazy to do it right now. But overall if the bike is stored for a few days without a tender, it will act up until it's gotten a chance to sit on said tender. Like I said, the charging system can currently keep a battery charged, just not re-charge one. As for bikes in dealerships, most of them sit with batterys out or unplugged.