Hi. I am trying to set a scene to automate my Extractor Fan with the humidity sensor. Scene set to switch the Fan on after a 10 minute delay works fine. Scene to switch the Fan off does not seem to work
What you need is: Inching feature. 
The supported device list in that document need update but the feature can work even for my old basicr2 too. 
It is very easy to setup, it can automatically switch off after x value of time after the switch on, but the x value is static.
In my situation (app), the inching feature not shown as scene but available in the device settings.
So yes, it may difficult to turn on and off the feature (because not a scene, it is a setting), and the value is static; fortunately for simple use case: switch off after x value of on; it can work. 