They reached a good enough point of 18 hours and spent any other gains in cutting costs. Same with their phones.

I get the expectation that people are always near chargers and I always carry a charger. That said, my 6 would be deep into reserve power before I get back to a charger probably once a week especially if I did any exercise in the day. It'd never last to the morning if I ever wore it without a solid charge.

Perhaps I am just too much of a power user or I don't sleep enough but the margin of error on the base watches doesn't seem sufficient for medical use.