I don't use the always on screen, and never really have on any watch with the option. I'm sure it would lessen the battery life, but I don't find it that useful. The raise to wake geasture if sufficient for me.3 Days of battery life with an always on screen??
Multiday battery life isn't important to me from the stand point of using it for multiple days without charging (though not needing to pack a charger for an overnight trip is night). I find watches too uncomfortable to sleep with, so charging overnight isn't an inconvenience.
Multiday battery life to me means that I can get up a 5am, go for a lengthy run, and use the watch until 12 am and still have plenty room to spare. Not having to worry about the battery only heavy days, or weekend trips is nice.