Time to talk battery capacities and long term results.
It's been what 4 months now and I've been running AccuBattery since day 1. I also ran it on my S7 edge and that phone lost 26% capacity when fully charged after 14 months. The S8+ afterr 4 months has lost 1%:
Worth noting that I only use fast charging, both wired and wireless (wireless mostly). And from the screenshot, you can see most of my charging is done from a lower remaining percentage as opposed to the typically recommended higher values where a brief top up from say 60% to 80% is advised to keep good battery health with other phones.
I believe only Sony Xperia phones have another type of intelligent battery charging system that charges at decelerated rates during night-time hours when you're typically in bed asleep to prolong long term battery capacity.
So by the time 14 months elapses, I fully expect the S8+ to have only lost 4-5% capacity when fully charged. Samsung's claim that the S8s only lose 5% after a year's worth of charging is completely true as far as I can see, and this makes me extremely happy.