I considered this when I first wrote the application and attempted to implement it.
However what is default?
Do I return the mode to whatever it was when I started running the application?
Do I return it to a fixed "ondemand" setting?
What happens if I cannot change it back?
What happens if a different piece of software changes the default outside of liqbase?
What happens if liqbase crashes?

How doesthe user know what mode it will be in depending upon what situation hes in.
You are considering the performance setting, but I have found myself setting to "powersave" prior to closing and locking my device - I want to ensure my battery lasts maximum possible duration and want it to be left afterwards.

A lot more questions and complications arise than simply giving the option to revert it which is why I left the setting as open as possible.

I understand the desire to return to some setting and if consensus agrees will put in place a "try to return to 'XXXX' when closing" option somewhere in the system.



As an aside, for a long time I ran a modified version of acmonitor which would set the ondemand/performance automatically when the nokia detected Charging/Battery status. this worked better than anything I could come up with for a single app.