I have to say after a couple of months of ownership of the Note 9, it doesn't live up to the hype of "all day battery life".
Don't get me wrong, I love this phone. But I feel now a bit naive thinking because of the 4000 mAh battery it would give me super battery life. I would describe it as "good but not great". But it does recharge nice and quick which I love. In the end I'm not complaining, just making a statement.
But standby drain is particularly bad. I've also had a number of times now the phone was running unusually warm and draining particularly badly, (not playing games) and I've powered off the phone and restarted it. It's happened about 3 times in about 2 months and happened again earlier today. I was watching some YouTube and even put the display brightness to bare minimum. But it persisted to run warm.
I'm really now hanging out for Android P to hopefully rectify some glitches I have experienced.