That's what APPLE says.Not true. 7 hours as a WORKOUT tracker, which means the heart-rate monitor is in constant use.
Nobody is going to monitor their heart-rate for 7 continuous hours. You can easily monitor it in intervals. The watch lasts all day tracking steps, standing, heart-rate, etc.
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Yes, the rules say you can only charge your watch at night when you should be sleeping. It's impossible to charge it at any other time. That's what the rules say.
Charge it overnight.
Wear it all day.
You’ll want to use Apple Watch all day long. So we gave it a battery that lasts up to 18 hours and made charging it at the end of the day utterly effortless. In fact, our goal was to make Apple Watch easy to charge in the dark. Without looking. While being only partially awake. We arrived at a solution that combines our MagSafe technology with inductive charging. It’s a completely sealed system free of exposed contacts. And it’s very forgiving, requiring no precise alignment. You simply hold the connector near the back of the watch, where magnets cause it to snap into place automatically.
This is no more than "if you can't fix it, feature it". Obviously you can charge it some other time, but then you give up that time during the day and lose the use of your $600 toy until it's charged.