A while back there was a discussion about tracking machine hours for maintenance. I have upadted my screen to track totalhours, spindlehours, X, Y, and Z axis travel, and a user defined maintenance variable (for example if you want to track how much machine time you had since the last time you greased your bearings).
I also added some runtime tracking of Gcode completion (% complete, ect.) ot the File Ops tab. Credit for some of that code goes to Dan Bishop.
Feel free to use the screen or any elements of it if you find it useful.