How can I prolong the battery life on my old Apple Watch Sport (1st gen)?

[blanketdown]

I have already turned on power reserve (which will show just the current time).
Is there a way to turn off the automatic lighting up of the display when I flick my wrist? Is there a way to have the watch's display turn on only when I either:
-- double tap the face
or
-- tab one of the hardware buttons?

How else can I prolong battery life?

 

[Night Spring]

Turn on theater mode.

I think there was also an option somewhere in the settings to turn off flick wrist to turn on display.