How long can I wear my Apple Watch before it needs charging?
AApple Watch-how long can it be worn without charging?
Depends on your usage patterns. I tested my daughter's while she was home from college over the Christmas break, and I was able to use it all day and still have ample battery left when I went to bed for the night. I charged it overnight for the next day. I believe the Apple specs say they expect 18 hours.
Mine also lasts all day with plenty to spare. My waking hours usually work out to be around 18 hours. I pop it on the charger overnight and it's always ready to go in the morning.
If you want to log your sleep with one of the apps available, they recommend charging the watch for a couple of hours in the evening then putting it on Airplane mode overnight. Personally, I don't find any of the sleep monitoring apps for the Apple Watch work well enough to justify this extra trouble.