Here's another thing I'm seeing common in Goodwill stores across the land. Those 30-pin 'iHome' speaker dock/clock radio combos. Great way of reusing an older iPod or iPhone.
As with any smart device I've experienced, a smart watch battery will last a lifetime if you avoid this:
1. Leaving it on the charging dock for overnight/days
2. Keeping it out of extremes (gasoline, dirt, abuse)
3. Charging it before the battery reaches less than 30% and unplugging the charge when it's close to 99%
Even then, a dead Apple Watch can still be a nifty nightstand clock on the dock in Nightstand Mode.