The Apple Watch display defaults to staying on and active for 15 seconds when the screen is tapped or activated.
With new versions of WatchOS you can choose to keep the Apple Watch screen on for considerably longer before it dims itself again. This is helpful for many situations.
How to Change How Long the Apple Watch Display Stays On For
You will need at least WatchOS 2 or later to be installed before you will find the option in the settings. If you don’t find the option in Settings, you’ll need to update WatchOS first.
Step 1. Open the Watch app on the paired iPhone and go to My Watch settings
Step 2. Go to General then go to Wake Screen
Step 3. Locate the On Tap section of Wake Screen settings and select Wake for 70 Seconds
Step 4. Exit out of Settings
The change is immediate and you can tap on the Watch screen to verify that the display will now stay active for considerably longer when it is tapped to activate.
You can always change this back to the default of 15 Seconds by returning to the Wake Screen settings and selecting that option.
While this is obviously useful but the biggest downside to making this Wake Screen adjustment is that you may notice bad battery.