I don’t think the battery life “doubles”. Probably just 10-15% or so but you lose a very important feature. Raising the arm to see the time is a very impolite and awkward gesture.
Impolite gesture?
I'd figure in a business meeting or a date looking at one's smartphone is a lot more impolite, even rude. In a business meeting you could just be prudent on keeping the flow of the meeting on schedule. I've seen executives, project managers, directors and even managers do this during meetings they're not hosting or leading. Nobody ever stated it was impolite - and this is at a national bank, 2nd largest and 1st largest gold producer in the world and a research company.
On my S6 turning off always on display saves about 4-5hrs battery life with the same use case, notification settings and things I use the watch for. Not sure if that would be the same on S7 though. Notifications definitely (especially social media notifications) rob the watch battery.