I have the same watch, but luckily none of the charging problems you're describing. Have had it for about 3 months now and it's been great.. fingers crossed it stays that way.
I'm not sure why companies do what you're describing. I've had the same with Dell - they've replaced the LCD on my laptop twice, and next step is apparently motherboard. Each time sending someone to my house to do the repairs. Surely this has been a lot more costly for them than just replacing with another laptop, as I imagine it would be for Samsung to replace your watch!
For sure. I can understand spending some time trying to fix something reasonably expensive, but this seems to be heading to a point where it's uneconomic for them to keep playing with it.