My Mate 9 battery is still super good, sometimes whole day battery only due 15%,really super...usage only whatapps and internet surfing.
Good for you.
Mine is OK, if left untouch, at least 4 days standby with ~30%. When using as hotspot oversea, 50% before bedtime. So not too bad, way better than HTC10 which drop to ~30% at 3pm as hotspot. Actually I have no idea if they had changed the battery, the mobo is still the old one though, IMEIs are the same.
Either way, I think the Mate 9 is still as good as current mid range phone. I'm really surprise it didn't lag as my other old phones. eg, HTC10 with SD820 lagggg even after factory reset; much more responsive than Sam A9Pro with SD652, MiMax with SD650, as good as VIVO V11 with SD660. Everyday using is smooth, opening any apps, eg, camera; the best is app installing and updating, almost instant after download complete.
I seriously happy with Huawei, used to be HTC sense UI fan. Have 2x HTC10, E8, Desire Eyes, Butterfly 1 & 2, THE one M7...now replaced all of them with Mate 9, Mate 10, P20 Pro, Mate 20 and Mate 20X. Too bad the P30 Pro is curved, hope the Mate 30 will stay flat but use the Pro cameras.