The policy has been recently extended to cover devices for three years after their original purchase date.
Apple has determined that under certain conditions on some first-generation Apple Watch devices the back cover may separate from the watch case. Apple will service eligible devices free of charge. Apple will authorize coverage for three years from the date of purchase.
Late last year Daring Fireball's John Gruber posted an image of his wife's Apple Watch that had come apart saying, "I sure hope Apple uses better glue for their cars than they do for their watches. That’s my wife’s Apple Watch, from May 2015. Workout readings have been erratic lately. Yesterday it came apart taking it off the charger."
Check out the image below. If your Apple Watch has come apart you can make a Genius Bar appointment, visit an authorized service provider, or contact Apple Support to request a repair.