My 6s came off the charger at 5:30 am and is now 92% at 9 pm. I didn't use it much at 40 mins use with calls, text, and browsing on wifi but that's what I need is for the battery to be steady and ready for when work calls for it.
I'd say standby is great considering having some weak cell service throughout and an active motion sensor. Some devices I'd had would drain 10% using a pedometer app through the workday or just sitting overnight so I'm happily impressed by it. Made it 4 days on one charge once. I do carry 2 phones and am light use between devices including iPod, other phones w/o sims and desktops.