I've got a 9, always on display is on (it's off 11pm to 7am), wear it except for the hour or so in the evening it's charging, usually about 40% when I charge.
If I forget to charge, can get around 36 hours or so on a full charge, without a workout, probably less with one.
if I turned off always on, might get another hour or 2 out of it, but probably not enough to get a full second day (without causing battery anxiety towards the end)
Also the 9 has fast charge that the 5 doesn't, will get you to full in about an hour or so (around 1.5 to 2 times as fast). You do need to use apple's USB-C cord, or if using a charge stand, make sure it specifies fast charge, quite a few stands support mag-safe for the phone, but have "slow charge" for the watch.