You should check out the watch app Staylit Wear from the google play store. Staylit has been mentioned here in the community several times and seems to be the go-to app for extending display time. The app is very simple to use and is easy to get to in the app drawer on your watch. Just go to the Google App Store with your watch, download, and install.
As you use the app, it will appear as recent at the top of the app list.
Staylit lets you pick the display duration by just sliding the choices up of down. The choices are:
OFF (watch default)
5, 6, 7, 8, 9, seconds
10, 15, 20, 25 seconds
30, 60 seconds
2, 3, 5 minutes and indefinitely.
So here's what I started doing... When I'm home not doing anything, watching TV, etc. I have Staylit set at the shortest time - 5 seconds - to conserve battery. However, if I'm heading out to a party or something cool, I get a good charge, turn up the brightness, and extend Staylit to 30 seconds to "show off" my designs. As I talk to people and wave my arms around (I'm Italian - I can't talk without moving my arms), the watch displays frequently and almost always becomes part of a conversation. Pretentious yes, but it's still cool.
Hope that helps,