I've had my watch about a month or so now and I've noticed that some days the battery only lasts a few hours. Has anyone else had this rapid draining or know of a fix?
I have a Galaxy Watch 3 but had the same problem and I think I found the culprit. For me, the proximity between the paired phone and the watch definitely impacts battery drain.
Somedays I carry my phone and some days I leave it on my desk. I found that when I'm more than 25 feet away from the phone the watch battery drops very fast (5-10% per hour) but when I carry the phone the battery drain is only about 2% per hour.
I used to charge my phone overnight in my office and found the watch (which I was wearing) would be nearly dead by morning. Moving the charger to the nightstand solved that problem.
Obviously it shouldn't be necessary to carry the phone with an LTE watch, but this observation explained what I was seeing.
Of course YMMV.