In my experience, connectivity and re-connection depends much more on the smartphone.
Older Galaxies, for instance, will chew up battery and have a tough time reconnecting. My Moto X, on the other hand, happily reconnects to both my Android Wear and Martian Notifiers when they come back into range.
Every watch does this at times. Even the Apple Watch.
It's why I prefer my LG Watch R, with its bright always-on face that lasts way over a full day (and usually two). The only time it seems to turn off, is after I've been in deep motionless sleep for a while, with the watch under my pillow. However, after I wake up and start using it again, it stays on all day.