If a certain configurable amount of screen time for the day or week or whatever configurable amount of time is exceeded, a session would then begin.
Actually you can do this!
- Go to Limits tab on Opal
- Open Apps
- Select All Apps & Categories (at the top). That basically means will count any screen time on your phone
- Choose a Time Limit, (for example 3 hours)
When you reach 3 hours of overall screen time, everything will be blocked.
Does this help?