It seems, with firmware 2.5, that WatchClockSkin gets special treatment in the background cleaner. If I try to add it to the apps excluded from battery saver, it is immediately switched on again.
In this video I demonstrate that every time I return to battery saver, it is switched on. I also show that when I switch off other apps, they are permanently off.
This means that my watchface is killed now and then, which is of course a bad experience, and even very bad if you were running a timer in the watchface, as you loose the information of how much time was left…